fbdev: add fb_read/fb_write functions for framebuffers in system RAM

The functions fb_read() and fb_write in fbmem.c assume that the framebuffer
is in IO memory.  However, we have 3 drivers (hecubafb, arcfb, and vfb)
where the framebuffer is allocated from system RAM (via vmalloc). Using
__raw_read/__raw_write (fb_readl/fb_writel) for these drivers is
illegal, especially in other platforms.

Create file read and write methods for these types of drivers.  These are
named fb_sys_read() and fb_sys_write().
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/Kconfig

@@ -122,6 +122,11 @@ config FB_SYS_IMAGEBLIT
 	  blitting. This is used by drivers that don't provide their own
 	  (accelerated) version and the framebuffer is in system RAM.
 
+config FB_SYS_FOPS
+       tristate
+       depends on FB
+       default n
+
 config FB_DEFERRED_IO
 	bool
 	depends on FB

drivers/video/Makefile

@@ -21,6 +21,7 @@ obj-$(CONFIG_FB_CFB_IMAGEBLIT) += cfbimgblt.o
 obj-$(CONFIG_FB_SYS_FILLRECT)  += sysfillrect.o
 obj-$(CONFIG_FB_SYS_COPYAREA)  += syscopyarea.o
 obj-$(CONFIG_FB_SYS_IMAGEBLIT) += sysimgblt.o
+obj-$(CONFIG_FB_SYS_FOPS)      += fb_sys_fops.o
 obj-$(CONFIG_FB_SVGALIB)       += svgalib.o
 obj-$(CONFIG_FB_MACMODES)      += macmodes.o
 obj-$(CONFIG_FB_DDC)           += fb_ddc.o

drivers/video/fb_sys_fops.c

+/*
+ * linux/drivers/video/fb_sys_read.c - Generic file operations where
+ * framebuffer is in system RAM
+ *
+ * Copyright (C) 2007 Antonino Daplas <adaplas@pol.net>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ *
+ */
+#include <linux/fb.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+
+ssize_t fb_sys_read(struct fb_info *info, char __user *buf, size_t count,
+		    loff_t *ppos)
+{
+	unsigned long p = *ppos;
+	void *src;
+	int err = 0;
+	unsigned long total_size;
+
+	if (info->state != FBINFO_STATE_RUNNING)
+		return -EPERM;
+
+	total_size = info->screen_size;
+
+	if (total_size == 0)
+		total_size = info->fix.smem_len;
+
+	if (p >= total_size)
+		return 0;
+
+	if (count >= total_size)
+		count = total_size;
+
+	if (count + p > total_size)
+		count = total_size - p;
+
+	src = (void __force *)(info->screen_base + p);
+
+	if (info->fbops->fb_sync)
+		info->fbops->fb_sync(info);
+
+	if (copy_to_user(buf, src, count))
+		err = -EFAULT;
+
+	if  (!err)
+		*ppos += count;
+
+	return (err) ? err : count;
+}
+EXPORT_SYMBOL_GPL(fb_sys_read);
+
+ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
+		     size_t count, loff_t *ppos)
+{
+	unsigned long p = *ppos;
+	void *dst;
+	int err = 0;
+	unsigned long total_size;
+
+	if (info->state != FBINFO_STATE_RUNNING)
+		return -EPERM;
+
+	total_size = info->screen_size;
+
+	if (total_size == 0)
+		total_size = info->fix.smem_len;
+
+	if (p > total_size)
+		return -EFBIG;
+
+	if (count > total_size) {
+		err = -EFBIG;
+		count = total_size;
+	}
+
+	if (count + p > total_size) {
+		if (!err)
+			err = -ENOSPC;
+
+		count = total_size - p;
+	}
+
+	dst = (void __force *) (info->screen_base + p);
+
+	if (info->fbops->fb_sync)
+		info->fbops->fb_sync(info);
+
+	if (copy_from_user(dst, buf, count))
+		err = -EFAULT;
+
+	if  (!err)
+		*ppos += count;
+
+	return (err) ? err : count;
+}
+EXPORT_SYMBOL_GPL(fb_sys_write);
+
+MODULE_AUTHOR("Antonino Daplas <adaplas@pol.net>");
+MODULE_DESCRIPTION("Generic file read (fb in system RAM)");
+MODULE_LICENSE("GPL");

include/linux/fb.h

@@ -903,6 +903,10 @@ extern void cfb_imageblit(struct fb_info *info, const struct fb_image *image);
 extern void sys_fillrect(struct fb_info *info, const struct fb_fillrect *rect);
 extern void sys_copyarea(struct fb_info *info, const struct fb_copyarea *area);
 extern void sys_imageblit(struct fb_info *info, const struct fb_image *image);
+extern ssize_t fb_sys_read(struct fb_info *info, char __user *buf,
+			   size_t count, loff_t *ppos);
+extern ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
+			    size_t count, loff_t *ppos);
 
 /* drivers/video/fbmem.c */
 extern int register_framebuffer(struct fb_info *fb_info);