[PATCH] fbdev: Fix return error of fb_write

["Antonino A. Daplas" <adaplas@gmail.com>]

Fix return code of fb_write():

If at least 1 byte was transferred to the device, return number of bytes,
otherwise:

    - return -EFBIG - if file offset is past the maximum allowable offset or
      size is greater than framebuffer length
    - return -ENOSPC - if size is greater than framebuffer length - offset

Signed-off-by: Antonino Daplas <adaplas@pol.net>
---

Andrew Morton wrote:
> "Antonino A. Daplas" <adaplas@gmail.com> wrote:
>> Richard Purdie wrote:
>>
>> - return -EFBIG if file offset is past the maximum allowable offset
> 
> OK.
> 
>> - return -EFBIG and write to end of framebuffer if size is bigger than the
>>   framebuffer length
> 
> We should return the number of bytes written in this case.
> 
>> - return -ENOSPC and write to end of framebuffer if size is bigger than the
>>   framebuffer length - file offset
> 
> Also here.
> 
> 
> If we can transfer _any_ bytes, we should do so, then return the number of
> bytes transferred.  If no bytes were transferrable then we should return
> -Ewhatever.
> 
> 

Okay, here's try #2:

 drivers/video/fbmem.c |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 944855b..a4b6776 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -669,13 +669,19 @@ fb_write(struct file *file, const char _
 		total_size = info->fix.smem_len;
 
 	if (p > total_size)
-		return 0;
+		return -EFBIG;
 
-	if (count >= total_size)
+	if (count > total_size) {
+		err = -EFBIG;
 		count = total_size;
+	}
+
+	if (count + p > total_size) {
+		if (!err)
+			err = -ENOSPC;
 
-	if (count + p > total_size)
 		count = total_size - p;
+	}
 
 	buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
 			 GFP_KERNEL);
@@ -717,7 +723,7 @@ fb_write(struct file *file, const char _
 
 	kfree(buffer);
 
-	return (err) ? err : cnt;
+	return (cnt) ? cnt : err;
 }
 
 #ifdef CONFIG_KMOD
-
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