If you enable group or project quotas on an XFS file system, then the
mount table presented through /proc/self/mounts erroneously shows
that both options are in effect for the file system.  The root of
the problem is some bad logic in the xfs_showargs() function, which
is used to format the file system type-specific options in effect
for a file system.

The problem originated in this GIT commit:
    Move platform specific mount option parse out of core XFS code
    Date: 11/22/07
    Author: Dave Chinner
    SHA1 ID: a67d7c5f

For XFS quotas, project and group quota management are mutually
exclusive--only one can be in effect at a time.  There are two
parts to managing quotas:  aggregating usage information; and
enforcing limits.  It is possible to have a quota in effect
(aggregating usage) but not enforced.

These features are recorded on an XFS mount point using these flags:
    XFS_PQUOTA_ACCT - Project quotas are aggregated
    XFS_GQUOTA_ACCT - Group quotas are aggregated
    XFS_OQUOTA_ENFD - Project/group quotas are enforced

The code in error is in fs/xfs/linux-2.6/xfs_super.c:

        if (mp->m_qflags & (XFS_PQUOTA_ACCT|XFS_OQUOTA_ENFD))
                seq_puts(m, "," MNTOPT_PRJQUOTA);
        else if (mp->m_qflags & XFS_PQUOTA_ACCT)
                seq_puts(m, "," MNTOPT_PQUOTANOENF);

        if (mp->m_qflags & (XFS_GQUOTA_ACCT|XFS_OQUOTA_ENFD))
                seq_puts(m, "," MNTOPT_GRPQUOTA);
        else if (mp->m_qflags & XFS_GQUOTA_ACCT)
                seq_puts(m, "," MNTOPT_GQUOTANOENF);

The problem is that XFS_OQUOTA_ENFD will be set in mp->m_qflags
if either group or project quotas are enforced, and as a result
both MNTOPT_PRJQUOTA and MNTOPT_GRPQUOTA will be shown as mount
options.
Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>

xfs_inobt_lookup is also used in xfs_itable.c, remove the STATIC modifier
from it's declaration to fix non-debug builds.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Fix a small typo in the compat ioctl handler that cause the swapext
compat handler to never be called.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Torsten Kaiser <just.for.lkml@googlemail.com>
Tested-by: Torsten Kaiser <just.for.lkml@googlemail.com>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

xfs_trans_iget is a wrapper for xfs_iget that adds the inode to the
transaction after it is read.  Except when the inode already is in the
inode cache, in which case it returns the existing locked inode with
increment lock recursion counts.

Now, no one in the tree every decrements these lock recursion counts,
so any user of this gets a potential double unlock when both the original
owner of the inode and the xfs_trans_iget caller unlock it.  When looking
back in a git bisect in the historic XFS tree there was only one place
that decremented these counts, xfs_trans_iput.  Introduced in commit
ca25df7a840f426eb566d52667b6950b92bb84b5 by Adam Sweeney in 1993,
and removed in commit 19f899a3ab155ff6a49c0c79b06f2f61059afaf3 by
Steve Lord in 2003.  And as long as it didn't slip through git bisects
cracks never actually used in that time frame.

A quick audit of the callers of xfs_trans_iget shows that no caller
really relies on this behaviour fortunately - xfs_ialloc allows this
inode from disk so it must not be there before, and all the RT allocator
routines only every add each RT bitmap inode once.

In addition to removing lots of code and reducing the size of the inode
item this patch also avoids the double inode cache lookup in each
create/mkdir/mknod transaction.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

The guarantees for O_SYNC are exactly the same as the ones we need to
make for an fsync call (and given that Linux O_SYNC is O_DSYNC the
equivalent is fdadatasync, but we treat both the same in XFS), except
with a range data writeout.  Jan Kara has started unifying these two
path for filesystems using the generic helpers, and I've started to
look at XFS.

The actual transaction commited by xfs_fsync and xfs_write_sync_logforce
has a different transaction number, but actually is exactly the same.
We'll only use the fsync transaction going forward.  One major difference
is that xfs_write_sync_logforce never issues a cache flush unless we
commit a transaction causing that as a side-effect, which is an obvious
bug in the O_SYNC handling.  Second all the locking and i_update_size
vs i_update_core changes from 978b7237
never made it to xfs_write_sync_logforce, so we add them back.

To make xfs_fsync easily usable from the O_SYNC path, the filemap_fdatawait
call is moved up to xfs_file_fsync, so that we don't wait on the whole
file after we already waited for our portion in xfs_write.

We'll also use a plain call to filemap_write_and_wait_range instead
of the previous sync_page_rang which did it in two steps including
an half-hearted inode write out that doesn't help us.

Once we're done with this also remove the now useless i_update_size
tracking.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Don't search too far - abort if it is outside a certain radius and simply do
a linear search for the first free inode.  In AGs with a million inodes this
can speed up allocation speed by 3-4x.

[hch: ported to the new xfs_ialloc.c world order]
Signed-off-by: Dave Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Currenly we have a xfs_inobt_lookup* variant for each comparism direction,
and all these get all three fields of the inobt records passed, while the
common case is just looking for the inode number and we have only marginally
more callers than xfs_inobt_lookup* variants.

So opencode a direct call to xfs_btree_lookup for the single case where we
need all fields, and replace xfs_inobt_lookup* with a xfs_inobt_looku that
just takes the inode number and the direction for all other callers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Clarify the control flow in xfs_dialloc.  Factor out a helper to go to the
next node from the current one and improve the control flow by expanding
composite if statements and using gotos.

The xfs_ialloc_next_rec helper is borrowed from Dave Chinners dynamic
allocation policy patches.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Factor out a common helper from repeated debug checks in xfs_dialloc and
xfs_difree.

[hch: split out from Dave's dynamic allocation policy patches]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Both callers of xfs_inobt_update have the record in form of a
xfs_inobt_rec_incore_t, so just pass a pointer to it instead of the
individual variables.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Most callers of xfs_inobt_get_rec need to fill a xfs_inobt_rec_incore_t, and
those who don't yet are fine with a xfs_inobt_rec_incore_t, instead of the
three individual variables, too.  So just change xfs_inobt_get_rec to write
the output into a xfs_inobt_rec_incore_t directly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Factor out code to initialize new inode clusters into a function of it's own.
This keeps xfs_ialloc_ag_alloc smaller and better structured and enables a
future inode cluster initialization transaction.  Also initialize the agno
variable earlier in xfs_ialloc_ag_alloc to avoid repeated byte swaps.

[hch:  The original patch is from Dave from his unpublished inode create
 transaction patch series, with some modifcations by me to apply stand-alone]
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

bp was tested for NULL a few lines before, followed by a return, and there
is no intervening modification of its value.

A simplified version of the semantic match that finds this problem is as
follows: (http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@r exists@
local idexpression x;
expression E;
position p1,p2;
@@

if (x == NULL || ...) { ... when forall
   return ...; }
... when != \(x=E\|x--\|x++\|--x\|++x\|x-=E\|x+=E\|x|=E\|x&=E\|&x\)
(
*x == NULL
|
*x != NULL
)
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Acked-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

Commit a19d9f88 removed the
ino64 option but left the XFS_INO64_OFFSET define it used
in place - just remove it.
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

CONFIG_XFS_DEBUG builds still need xfs_read_agf to be
non-static, oops.
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

A lot more functions could be made static, but they need
forward declarations; this does some easy ones, and also
found a few unused functions in the process.
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

The locking in xfs_iget_cache_hit currently has numerous problems:

 - we clear the reclaim tag without i_flags_lock which protects
   modifications to it
 - we call inode_init_always which can sleep with pag_ici_lock
   held (this is oss.sgi.com BZ #819)
 - we acquire and drop i_flags_lock a lot and thus provide no
   consistency between the various flags we set/clear under it

This patch fixes all that with a major revamp of the locking in
the function.  The new version acquires i_flags_lock early and
only drops it once we need to call into inode_init_always or before
calling xfs_ilock.

This patch fixes a bug seen in the wild where we race modifying the
reclaim tag.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

The locking in xfs_iget_cache_hit currently has numerous problems:

 - we clear the reclaim tag without i_flags_lock which protects
   modifications to it
 - we call inode_init_always which can sleep with pag_ici_lock
   held (this is oss.sgi.com BZ #819)
 - we acquire and drop i_flags_lock a lot and thus provide no
   consistency between the various flags we set/clear under it

This patch fixes all that with a major revamp of the locking in
the function.  The new version acquires i_flags_lock early and
only drops it once we need to call into inode_init_always or before
calling xfs_ilock.

This patch fixes a bug seen in the wild where we race modifying the
reclaim tag.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

drivers/md/dm-log-userspace-transfer.c:110: warning: format '%lu' expects type 'long unsigned int', but argument 4 has type 'size_t'

Previously posted and acked, but apparently lost.
http://lkml.indiana.edu/hypermail/linux/kernel/0906.2/02074.htmlSigned-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: dm-devel@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The triggered field of struct poll_wqueues introduced in commit
5f820f64 ("poll: allow f_op->poll to
sleep").

It was first set to 1 in pollwake() (now __pollwake() ), tested and
later set to 0 in poll_schedule_timeout(), but not initialized before.

As a result when the process needs to sleep, triggered was likely to be
non-zero even if pollwake() is not called before the first
poll_schedule_timeout(), meaning schedule_hrtimeout_range() would not be
called and an extra loop calling all ->poll() would be done.

This patch initialize triggered to 0 in poll_initwait() so the ->poll()
are not called twice before the process goes to sleep when it needs to.
Signed-off-by: Guillaume Knispel <gknispel@proformatique.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

* git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6-fixes:
  GFS2: Fix permissions on "recover" file

* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6: (38 commits)
  V4L/DVB (12441): siano: read buffer overflow
  V4L/DVB (12440): Use kzalloc for frontend states to have struct dvb_frontend properly
  V4L/DVB (12438): Read buffer overflow
  V4L/DVB (12437): dvb: siano uses/depends on INPUT
  V4L/DVB (12436): stk-webcam: read buffer overflow
  V4L/DVB (12432): em28xx: fix regression in Empire DualTV digital tuning
  V4L/DVB (12429): v4l2-ioctl: fix G_STD and G_PARM default handlers
  V4L/DVB (12428): hdpvr: add missing initialization of current_norm
  V4L/DVB (12424): soc-camera: fix recursive locking in .buf_queue()
  V4L/DVB (12422): media/zr364xx: fix build errors
  V4L/DVB (12405): em28xx-cards: move register 0x13 setting to the proper place
  V4L/DVB (12411): em28xx: Fix artifacts with Silvercrest webcam
  V4L/DVB (12410): em28xx: Move the non-board dependent part to be outside em28xx_pre_card_setup()
  V4L/DVB (12407): em28xx: Adjust Silvercrest xtal frequency
  V4L/DVB (12406): em28xx: fix: don't do image interlacing on webcams
  V4L/DVB (12403): em28xx: properly reports some em2710 chips
  V4L/DVB (12402): em28xx: fix: some em2710 chips use a different vendor ID
  V4L/DVB (12401): m9v011: add vflip/hflip controls to control mirror/upside down
  V4L/DVB (12400): em28xx: Allow changing fps on webcams
  V4L/DVB (12399): mt9v011: Add support for controlling frame rates
  ...

Although this file is only ever written and not read by
userspace, it seems that the utils are opening this
file O_RDWR, so we need to allow that.

Also fixes the whitespace which seemed to be broken.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: David Teigland <teigland@redhat.com>

With mode DEVICE_MODE_RAW_TUNER a read occurs past the end of smscore_fw_lkup[].
Subsequently an attempt is made to load the firmware from the resulting
filename.
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

This patch changes most frontend drivers to allocate their state structure via
kzalloc and not kmalloc. This is done to properly initialize the
embedded "struct dvb_frontend frontend" field, that they all have.

The visible effect of this struct being uninitalized is, that the member "id"
that is used to set the name of kernel thread is totally random.

Some board drivers (for example cx88-dvb) set this "id" via
videobuf_dvb_alloc_frontend but most do not.

So I at least get random id values for saa7134, flexcop and ttpci based cards.
It looks like this in dmesg:
DVB: registering adapter 1 frontend -10551321 (ST STV0299 DVB-S)

The related kernel thread then also gets a strange name
like "kdvb-ad-1-fe--1".

Cc: Michael Krufky <mkrufky@linuxtv.org>
Cc: Steven Toth <stoth@linuxtv.org>
Cc: Timothy Lee <timothy.lee@siriushk.com>
Cc: Igor M. Liplianin <liplianin@me.by>
Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Acked-by: Andreas Oberritter <obi@linuxtv.org>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

parport[n] is checked before n < MAX_CAMS
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

siano uses input_*() functions so it should depend on INPUT
to prevent build errors:

ERROR: "input_event" [drivers/media/dvb/siano/sms1xxx.ko] undefined!
ERROR: "input_register_device" [drivers/media/dvb/siano/sms1xxx.ko] undefined!
ERROR: "input_free_device" [drivers/media/dvb/siano/sms1xxx.ko] undefined!
ERROR: "input_unregister_device" [drivers/media/dvb/siano/sms1xxx.ko] undefined!
ERROR: "input_allocate_device" [drivers/media/dvb/siano/sms1xxx.ko] undefined!

Cc: Michael Krufky <mkrufky@linuxtv.org>
Cc: Uri Shkolnik <uris@siano-ms.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

It tested the value of stk_sizes[i].m before checking whether i was in range.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Restore support for digital tuning caused by regression during introduction
of disable_i2c_gate parameter to zl10353 driver.

Thanks to user "Xwang" for reporting the problem and testing the fix

Cc: Xwang <xwang1976@email.it>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

The v4l core supplies default handlers for G_STD and G_PARM. However, both
default handlers are buggy.

This patch fixes the following:

1) If no g_std is supplied and current_norm == 0, then this driver does not
   support TV video standards (e.g. a radio or webcam driver). Return
   -EINVAL. This ensures that there is no bogus VIDIOC_G_STD support for
   such drivers.

2) The default VIDIOC_G_PARM handler used current_norm instead of first
   checking if the driver supported g_std and calling that to get the norm.
   It also didn't check if current_norm was 0, since in that case the driver
   does not support TV standards (or no standard was set at all) and the
   default handler should return -EINVAL.

Note that I am very unhappy with these default handlers: I think they
basically behave like some very strange and unexpected side-effect.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Drivers should either set current_norm or supply a g_std callback.

The hdpvr driver does neither. Since it initializes to a 60 Hz format
I've initialized the current_norm to NTSC | PAL_M | PAL_60 which is the
60 Hz subset of tvnorms.

Cc: Janne Grunau <j@jannau.net>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

The .buf_queue() V4L2 driver method is called under
spinlock_irqsave(q->irqlock,...), don't take the lock again inside the
function.
Reported-by: Antonio Ospite <ospite@studenti.unina.it>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Fix build errors in zr364xx by adding selects:

zr364xx.c:(.text+0x195ed7): undefined reference to `videobuf_streamon'
zr364xx.c:(.text+0x196030): undefined reference to `videobuf_dqbuf'
zr364xx.c:(.text+0x1960c4): undefined reference to `videobuf_qbuf'
zr364xx.c:(.text+0x196123): undefined reference to `videobuf_querybuf'
zr364xx.c:(.text+0x196182): undefined reference to `videobuf_reqbufs'
zr364xx.c:(.text+0x196224): undefined reference to `videobuf_queue_is_busy'
zr364xx.c:(.text+0x196390): undefined reference to `videobuf_vmalloc_free'
zr364xx.c:(.text+0x196571): undefined reference to `videobuf_iolock'
zr364xx.c:(.text+0x196678): undefined reference to `videobuf_mmap_mapper'
zr364xx.c:(.text+0x196760): undefined reference to `videobuf_poll_stream'
zr364xx.c:(.text+0x19689a): undefined reference to `videobuf_read_one'
zr364xx.c:(.text+0x1969ec): undefined reference to `videobuf_mmap_free'
zr364xx.c:(.text+0x197862): undefined reference to `videobuf_queue_vmalloc_init'
zr364xx.c:(.text+0x197a28): undefined reference to `videobuf_streamoff'
zr364xx.c:(.text+0x198203): undefined reference to `videobuf_to_vmalloc'
zr364xx.c:(.text+0x198603): undefined reference to `videobuf_streamoff'
drivers/built-in.o: In function `free_buffer':
zr364xx.c:(.text+0x19930c): undefined reference to `videobuf_vmalloc_free'
drivers/built-in.o: In function `zr364xx_open':
zr364xx.c:(.text+0x19a7de): undefined reference to `videobuf_queue_vmalloc_init'
drivers/built-in.o: In function `read_pipe_completion':
zr364xx.c:(.text+0x19b17f): undefined reference to `videobuf_to_vmalloc'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Register 0x13 seems to be a sort of image control, maybe gamma, white
level or black level. Lower values produce better images, while higher
values increases the contrast and shifts colors to green. 0xff produces
a black image. This register is not Silvercrest-specific, so its code
should be moved to a better place.

If this register is left alone, a random value can be found at the
register, producing weird results.

While here, let's remove register 0x0d, as it had no noticed effect at
the image.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Silvercrest mt9v011 sensor produces a 640x480 image. However,
previously, the code were getting only half of the lines and merging two
consecutive frames to "produce" a 640x480 image.

With the addition of progressive mode, now em28xx is working with a full
image. However, when the number of lines is bigger than 240, the
beginning of some odd lines are filled with blank.

After lots of testing, and physically checking the device for a Xtal, it
was noticed experimentally that mt9v011 is using em28xx XCLK as its
clock. Due to that, changing XCLK value changes the maximum speed of the
stream.

At the tests, it were possible to produce up to 32 fps, using a 30 MHz
XCLK. However, at that rate, the artifacts happen even at 320x240. Lower
values of XCLK produces artifacts only at 640x480.

At some values of xclk (for example XCLKK = 6 MHz, 640x480), it is
possible to see an invalid sucession of artifacts with this pattern:

.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
..xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
...xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
....xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
..xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
...xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
....xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

(where the dots represent the blanked pixels)

So, it seems that a waveform in the format of a ramp is interferring at
the image.

The cause of this interference is currently unknown. Some possibilities
are:
	- electrical interference (maybe this device is broken?);
	- some issue at mt9v011 programming;
	- some bug at em28xx chip.

So, for now, let's be conservative and use a value of XCLK that we know
for sure that it won't cause artifacts.

As I'm waiting for more of such devices with different em28xx chipset
revisions, I'll have the opportunity to double check the issue with
other pieces of hardware.

Later patches can vary XCLK depending on the vertical resolutions, if a
proper fix is not discovered.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

em28xx_pre_card_setup() is meant to contain board-specific initialization. Also,
as autodetection sometimes occur only after having i2c bus enabled, this
function may need to be called later.

Moving those setups to happen outside the function avoids calling it twice without
need and without duplicating output lines at dmesg.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

We don't know the xtal frequency of Silvercrest, but we need to have
some value in order to allow controlling the frame rate frequency. The
value is probably still wrong, since the manufacturer announces this
device as being capable of 30fps, but the maximum we can get is
13.5 fps.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Due to historical reasons, em28xx driver gets two consecutive frames and
fold them into an unique framing, doing interlacing. While this works
fine for TV images, this produces two bad effects with webcams:

1) webcam images are progressive. Merging two consecutive images produce
interlacing artifacts on the image;

2) since the driver needs to get two frames, it reduces the maximum
frame rate by two.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

As reported by hermann pitton <hermann-pitton@arcor.de>, some devices
has a different chip id for em2710 (likely the older ones):

em28xx: New device @ 480 Mbps (eb1a:2710, interface 0, class 0)
em28xx #0: Identified as EM2710/EM2750/EM2751 webcam grabber (card=22)
em28xx #0: em28xx chip ID = 17
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>