Defined some const arrays as static since they don't need external linkage.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

The "address" member of struct ia_css_host_data is a pointer-to-char,
so define default as NULL.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/common/videobuf/videobuf2-core.c:2525:34-35: Unneeded semicolon

 Remove unneeded semicolon.

Generated by: scripts/coccinelle/misc/semicolon.cocci

Fixes: 03fbdb2f ("media: move videobuf2 to drivers/media/common")
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>

Most of the I2C headers got moved a long time ago to
include/media/i2c. Stop including them at the patch.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Except for DVB, all media kAPI headers are at include/media.

Move the headers to it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

The "reserved" field was a way, used at V4L2 API, to add new
data to existing structs without breaking userspace. However,
there are now clever ways of doing that, without needing to add
an uneeded overhead. So, get rid of them.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

5 new ioctls were added to the DVB demux API, in order to
handle memory maped I/O. Add documentation for them.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

With the new dmx mmap interface, those two syscalls are now
handled by the subsystem. Document them.

This patch is based on the V4L2 text for those ioctls.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Now that VB2 is used by both V4L2 and DVB core, move it to
the common part of the subsystem.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

This API is still experimental. Make it optional, allowing to
compile the code without it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Use trivial handling for the new DVB demux ioctls, as none
of them passes a pointer inside their structures.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

This code is released under GPL. Add the corresponding SPDX
headers.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

if the number of buffers requested by the user is too big, the
VB core will truncate to a valid value.

Use it, instead of what the user requested.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

It is not a good idea to let users to request a very high buffer
size.

So, add an upper limit.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

The streamoff logic is causing those warnings:

 WARNING: CPU: 3 PID: 3382 at drivers/media/v4l2-core/videobuf2-core.c:1652 __vb2_queue_cancel+0x177/0x250 [videobuf2_core]
 Modules linked in: bnep fuse xt_CHECKSUM iptable_mangle tun ebtable_filter ebtables ip6table_filter ip6_tables xt_physdev br_netfilter bluetooth bridge rfkill ecdh_generic stp llc nf_log_ipv4 nf_log_common xt_LOG xt_conntrack ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack libcrc32c sunrpc vfat fat snd_hda_codec_hdmi rc_dib0700_nec i915 rc_pinnacle_pctv_hd em28xx_rc a8293 ts2020 m88ds3103 i2c_mux em28xx_dvb dib8000 dvb_usb_dib0700 dib0070 dib7000m dib0090 dvb_usb dvb_core uvcvideo snd_usb_audio videobuf2_v4l2 dib3000mc videobuf2_vmalloc videobuf2_memops dibx000_common videobuf2_core rc_core snd_usbmidi_lib snd_rawmidi em28xx tveeprom v4l2_common videodev media intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp snd_hda_intel
 kvm_intel snd_hda_codec kvm snd_hwdep snd_hda_core snd_seq irqbypass crct10dif_pclmul crc32_pclmul i2c_algo_bit ghash_clmulni_intel snd_seq_device drm_kms_helper snd_pcm intel_cstate intel_uncore snd_timer tpm_tis drm mei_wdt iTCO_wdt iTCO_vendor_support tpm_tis_core snd intel_rapl_perf mei_me mei tpm i2c_i801 soundcore lpc_ich video binfmt_misc hid_logitech_hidpp hid_logitech_dj e1000e crc32c_intel ptp pps_core analog gameport joydev
 CPU: 3 PID: 3382 Comm: lt-dvbv5-zap Not tainted 4.14.0+ #3
 Hardware name:                  /D53427RKE, BIOS RKPPT10H.86A.0048.2017.0506.1545 05/06/2017
 task: ffff94b93bbe1e40 task.stack: ffffb7a98320c000
 RIP: 0010:__vb2_queue_cancel+0x177/0x250 [videobuf2_core]
 RSP: 0018:ffffb7a98320fd40 EFLAGS: 00010202
 RAX: 0000000000000001 RBX: ffff94b92ff72428 RCX: 0000000000000000
 RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffff94b92ff72428
 RBP: ffffb7a98320fd68 R08: ffff94b92ff725d8 R09: ffffb7a98320fcc8
 R10: ffff94b978003d98 R11: ffff94b92ff72428 R12: ffff94b92ff72428
 R13: 0000000000000282 R14: ffff94b92059ae20 R15: dead000000000100
 FS:  0000000000000000(0000) GS:ffff94b99e380000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000555953007d70 CR3: 000000012be09004 CR4: 00000000001606e0
 Call Trace:
  vb2_core_streamoff+0x28/0x90 [videobuf2_core]
  dvb_vb2_stream_off+0xd1/0x150 [dvb_core]
  dvb_dvr_release+0x114/0x120 [dvb_core]
  __fput+0xdf/0x1e0
  ____fput+0xe/0x10
  task_work_run+0x94/0xc0
  do_exit+0x2dc/0xba0
  do_group_exit+0x47/0xb0
  SyS_exit_group+0x14/0x20
  entry_SYSCALL_64_fastpath+0x1a/0xa5
 RIP: 0033:0x7f775e931ed8
 RSP: 002b:00007fff07019d68 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
 RAX: ffffffffffffffda RBX: 0000000001d02690 RCX: 00007f775e931ed8
 RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001
 RBP: 00007fff0701a500 R08: 00000000000000e7 R09: ffffffffffffff70
 R10: 00007f775e854dd8 R11: 0000000000000246 R12: 0000000000000000
 R13: 00000000035fa000 R14: 000000000000000a R15: 000000000000000a
 Code: 00 00 04 74 1c 44 89 e8 49 83 c5 01 41 39 84 24 88 01 00 00 77 8a 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 bb fd ff ff eb da <0f> ff 41 8b b4 24 88 01 00 00 85 f6 74 34 bb 01 00 00 00 eb 10

There are actually two issues here:

1) list_del() should be called when changing the buffer state;

2) The logic with marks the buffers as done is at the wrong place.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Adds a new uAPI for DVB to use streaming I/O which is implemented
based on videobuf2, using those new ioctls:

- DMX_REQBUFS:  Request kernel to allocate buffers which count and size
	        are dedicated by user.
- DMX_QUERYBUF: Get the buffer information like a memory offset which
		will mmap() and be shared with user-space.
- DMX_EXPBUF:   Just for testing whether buffer-exporting success or not.
- DMX_QBUF:     Pass the buffer to kernel-space.
- DMX_DQBUF:    Get back the buffer which may contain TS data.

Originally developed by: Junghak Sung <jh1009.sung@samsung.com>, as
seen at:
	https://patchwork.linuxtv.org/patch/31613/
	https://patchwork.kernel.org/patch/7334301/

The original patch was written before merging VB2-core functionalities
upstream. When such series was added, several adjustments were made,
fixing some issues with	V4L2, causing the original patch to be
non-trivially rebased.

After rebased, a few bugs in the patch were fixed. The patch was
also enhanced it and polling functionality got added.

The main changes over the original patch are:

dvb_vb2_fill_buffer():
	- Set the size of the outgoing buffer after while loop using
	  vb2_set_plane_payload;

	- Added NULL check for source buffer as per normal convention
	  of demux driver, this is called twice, first time with valid
	  buffer second time with NULL pointer, if its not handled,
	  it will result in  crash

	- Restricted spinlock for only list_* operations

dvb_vb2_init():
	- Restricted q->io_modes to only VB2_MMAP as its the only
	  supported mode

dvb_vb2_release():
	- Replaced the && in if condiion with &, because otherwise
	  it was always getting satisfied.

dvb_vb2_stream_off():
	- Added list_del code for enqueud buffers upon stream off

dvb_vb2_poll():
	- Added this new function in order to support polling

dvb_demux_poll() and dvb_dvr_poll()
	- dvb_vb2_poll() is now called from these functions

- Ported this patch and latest videobuf2 to lower kernel versions and
  tested auto scan.
Co-developed-by: Junghak Sung <jh1009.sung@samsung.com>

[mchehab@s-opensource.com: checkpatch fixes]
Signed-off-by: Junghak Sung <jh1009.sung@samsung.com>
Signed-off-by: Geunyoung Kim <nenggun.kim@samsung.com>
Acked-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Acked-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Satendra Singh Thakur <satendra.t@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

* 'docs-next' of git://git.lwn.net/linux: (888 commits)
  w1_netlink.h: add support for nested structs
  scripts: kernel-doc: apply filtering rules to warnings
  scripts: kernel-doc: improve nested logic to handle multiple identifiers
  scripts: kernel-doc: handle nested struct function arguments
  scripts: kernel-doc: print the declaration name on warnings
  scripts: kernel-doc: get rid of $nested parameter
  scripts: kernel-doc: parse next structs/unions
  scripts: kernel-doc: replace tabs by spaces
  scripts: kernel-doc: change default to ReST format
  scripts: kernel-doc: improve argument handling
  scripts: kernel-doc: get rid of unused output formats
  docs: get rid of kernel-doc-nano-HOWTO.txt
  docs: kernel-doc.rst: add documentation about man pages
  docs: kernel-doc.rst: improve typedef documentation
  docs: kernel-doc.rst: improve structs chapter
  docs: kernel-doc.rst: improve function documentation section
  docs: kernel-doc.rst: improve private members description
  docs: kernel-doc.rst: better describe kernel-doc arguments
  docs: fix process/submit-checklist.rst Sphinx warning
  docs: ftrace-uses.rst fix varios code-block directives
  ...

Now that kernel-doc can hanle nested structs/unions, describe
such fields at w1_netlink_message_types.
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

When kernel-doc is called with output selection filters,
it will be called lots of time for a single file. If
there is a warning present there, it means that it may
print hundreds of identical warnings.

Worse than that, the -function NAME actually filters only
functions. So, it makes no sense at all to print warnings
for structs or enums.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

It is possible to use nested structs like:

struct {
	struct {
		void *arg1;
	} st1, st2, *st3, st4;
};

Handling it requires to split each parameter. Change the logic
to allow such definitions.

In order to test the new nested logic, the following file
was used to test

<code>
struct foo { int a; }; /* Just to avoid errors if compiled */

/**
 * struct my_struct - a struct with nested unions and structs
 * @arg1: first argument of anonymous union/anonymous struct
 * @arg2: second argument of anonymous union/anonymous struct
 * @arg1b: first argument of anonymous union/anonymous struct
 * @arg2b: second argument of anonymous union/anonymous struct
 * @arg3: third argument of anonymous union/anonymous struct
 * @arg4: fourth argument of anonymous union/anonymous struct
 * @bar.st1.arg1: first argument of struct st1 on union bar
 * @bar.st1.arg2: second argument of struct st1 on union bar
 * @bar.st1.bar1: bar1 at st1
 * @bar.st1.bar2: bar2 at st1
 * @bar.st2.arg1: first argument of struct st2 on union bar
 * @bar.st2.arg2: second argument of struct st2 on union bar
 * @bar.st3.arg2: second argument of struct st3 on union bar
 * @f1: nested function on anonimous union/struct
 * @bar.st2.f2: nested function on named union/struct
 */
struct my_struct {
   /* Anonymous union/struct*/
   union {
	struct {
	    char arg1 : 1;
	    char arg2 : 3;
	};
       struct {
           int arg1b;
           int arg2b;
       };
       struct {
           void *arg3;
           int arg4;
           int (*f1)(char foo, int bar);
       };
   };
   union {
       struct {
           int arg1;
           int arg2;
	   struct foo bar1, *bar2;
       } st1;           /* bar.st1 is undocumented, cause a warning */
       struct {
           void *arg1;  /* bar.st3.arg1 is undocumented, cause a warning */
	    int arg2;
          int (*f2)(char foo, int bar); /* bar.st3.fn2 is undocumented, cause a warning */
       } st2, st3, *st4;
       int (*f3)(char foo, int bar); /* f3 is undocumented, cause a warning */
   } bar;               /* bar is undocumented, cause a warning */

   /* private: */
   int undoc_privat;    /* is undocumented but private, no warning */

   /* public: */
   int undoc_public;    /* is undocumented, cause a warning */
};
</code>

It produces the following warnings, as expected:

test2.h:57: warning: Function parameter or member 'bar' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st1' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st2' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st3' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st3.arg1' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st3.f2' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st4' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st4.arg1' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st4.arg2' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st4.f2' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.f3' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'undoc_public' not described in 'my_struct'
Suggested-by: Markus Heiser <markus.heiser@darmarit.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Function arguments are different than usual ones. So, an
special logic is needed in order to handle such arguments
on nested structs.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

The logic at create_parameterlist()'s ancillary push_parameter()
function has already a way to output the declaration name, with
would help to discover what declaration is missing.

However, currently, the logic is utterly broken, as it uses
the var $type with a wrong meaning. With the current code,
it will never print anything. I suspect that originally
it was using the second argument of output_declaration().

I opted to not rely on a globally defined $declaration_name,
but, instead, to pass it explicitly as a parameter.

While here, I removed a unaligned check for !$anon_struct_union.
This is not needed, as, if $anon_struct_union is not zero,
$parameterdescs{$param} will be defined.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

The check_sections() function has a $nested parameter, meant
to identify when a nested struct is present. As we now have
a logic that handles it, get rid of such parameter.
Suggested-by: Markus Heiser <markus.heiser@darmarit.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

There are several places within the Kernel tree with nested
structs/unions, like this one:

  struct ingenic_cgu_clk_info {
    const char *name;
    enum {
      CGU_CLK_NONE = 0,
      CGU_CLK_EXT = BIT(0),
      CGU_CLK_PLL = BIT(1),
      CGU_CLK_GATE = BIT(2),
      CGU_CLK_MUX = BIT(3),
      CGU_CLK_MUX_GLITCHFREE = BIT(4),
      CGU_CLK_DIV = BIT(5),
      CGU_CLK_FIXDIV = BIT(6),
      CGU_CLK_CUSTOM = BIT(7),
    } type;
    int parents[4];
    union {
      struct ingenic_cgu_pll_info pll;
      struct {
        struct ingenic_cgu_gate_info gate;
        struct ingenic_cgu_mux_info mux;
        struct ingenic_cgu_div_info div;
        struct ingenic_cgu_fixdiv_info fixdiv;
      };
      struct ingenic_cgu_custom_info custom;
    };
  };

Currently, such struct is documented as:

	**Definition**

	::
	struct ingenic_cgu_clk_info {
	    const char * name;
	};

	**Members**

	``name``
	  name of the clock

With is obvioulsy wrong. It also generates an error:
	drivers/clk/ingenic/cgu.h:169: warning: No description found for parameter 'enum'

However, there's nothing wrong with this kernel-doc markup: everything
is documented there.

It makes sense to document all fields there. So, add a
way for the core to parse those structs.

With this patch, all documented fields will properly generate
documentation.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Sphinx has a hard time dealing with tabs, causing it to
misinterpret paragraph continuation.

As we're now mainly focused on supporting ReST output,
replace tabs by spaces, in order to avoid troubles when
the output is parsed by Sphinx.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Right now, if kernel-doc is called without arguments, it
defaults to man pages. IMO, it makes more sense to
default to ReST, as this is the output that it is most
used nowadays, and it easier to check if everything got
parsed fine on an enriched text mode format.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Right now, if one uses "--rst" instead of "-rst", it just
ignore the argument and produces a man page. Change the
logic to accept both "-cmd" and "--cmd". Also, if
"cmd" doesn't exist, print the usage information and exit.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Since there isn't any docbook code anymore upstream,
we can get rid of several output formats:

- docbook/xml, html, html5 and list formats were used by
  the old build system;
- As ReST is text, there's not much sense on outputting
  on a different text format.

After this patch, only man and rst output formats are
supported.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Everything there is already described at
Documentation/doc-guide/kernel-doc.rst. So, there's no reason why
to keep it anymore.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

kernel-doc-nano-HOWTO.txt has a chapter about man pages
production. While we don't have a working  "make manpages"
target, add it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add documentation about typedefs for function prototypes and
move it to happen earlier.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

There is a mess on this chapter: it suggests that even
enums and unions should be documented with "struct". That's
not the way it should be ;-)

Fix it and move it to happen earlier.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Move its contents to happen earlier and improve the description
of return values, adding a subsection to it. Most of the contents
there came from kernel-doc-nano-HOWTO.txt.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

The private members section can now be moved to be together
with the arguments section. Move it there and add an example
about the usage of public:
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add a new section to describe kernel-doc arguments,
adding examples about how identation should happen, as failing
to do that causes Sphinx to do the wrong thing.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

add missing indent whitespace to list item, fixes the warning:

- process/submit-checklist.rst:41: WARNING: Enumerated list ends without a blank
  line; unexpected unindent.
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Reviewed-by: Darren Hart (VMware) <dvhart@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

ftrace-uses.rst is not yet included into any toctree, but since it is
a .rst file, it is parsed by the Sphinx build. Thats, why we see some
WARNINGS:

- trace/ftrace-uses.rst:53: WARNING: Definition list ends without a blank line; unexpected unindent.
- trace/ftrace-uses.rst:89: WARNING: Inline emphasis start-string without end-string.
- trace/ftrace-uses.rst:89: WARNING: Inline emphasis start-string without end-strin

Fixing the code-block directives results in a less noisy build, but the 'not
included' WARNING will be stay:

- trace/ftrace-uses.rst: WARNING: document isn't included in any toctree
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

A reference to printk-formats.txt didn't get updated when the file moved;
fix that.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

`Documentation/i2c/dev-interface` gives examples for accessing i2c from
userspace.

There's a note that warns developers about the two `i2c-dev.h` header
files which were shipped with the kernel and i2c-tools separately.

However, following i2c-tools commits suggest that the header files are now
identical (in functionality) and `i2c_*` helper functions are now defined
in a separate header called `i2c/smbus.h`, which is distributed with
i2c-tools:

commit 652619121974 ("Minimize differences with kernel flavor")
commit 93caf007f4cb ("Move SMBus helper functions to include/i2c/smbus.h")

Thus, I've converted the warning paragraph into a historical note and
updated the suggested header files.
Signed-off-by: Cengiz Can <cengizc@gmail.com>
Cc: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Update Documentation/driver-api/usb/usb3-debug-port.rst. This update
includes the guide for using xHCI debug capability based TTY serial
link.

Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>