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media: vb2: use ssize_t for vb2_read/vb2_write

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vb2_read() and vb2_write() return size_t, but propagate
negative errno values from __vb2_perform_fileio().

This relies on implicit signed/unsigned conversions in callers
(e.g. vb2_fop_read()) to recover error codes:

    __vb2_perform_fileio() -> -EINVAL
    vb2_read()             -> (size_t)-EINVAL
    vb2_fop_read()         -> -EINVAL

This relies on implicit conversions that are not obvious.

These helpers are exported (EXPORT_SYMBOL_GPL) and part of the
vb2 API, so changing their return type may affect existing users.

However, they conceptually follow read/write semantics, where
ssize_t is typically used to return either a byte count or a
negative error code.

Switch vb2_read() and vb2_write() to ssize_t, and update
__vb2_perform_fileio() accordingly.

Signed-off-by: Zile Xiong <xiongzile99@gmail.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Fixes: b25748fe61 ("[media] v4l: videobuf2: add read() and write() emulator")
Cc: stable@vger.kernel.org
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
This commit is contained in:
Zile Xiong
2026-03-20 14:54:45 +08:00
committed by Hans Verkuil
parent 084973ebd6
commit a562d6dc86
2 changed files with 10 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/media/common/videobuf2/videobuf2-core.c
View File

@@ -2990,8 +2990,8 @@ static int __vb2_cleanup_fileio(struct vb2_queue *q)
* @nonblock: mode selector (1 means blocking calls, 0 means nonblocking)
* @read: access mode selector (1 means read, 0 means write)
*/
static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_t count,
loff_t *ppos, int nonblock, int read)
static ssize_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_t count,
loff_t *ppos, int nonblock, int read)
{
struct vb2_fileio_data *fileio;
struct vb2_fileio_buf *buf;
@@ -3154,15 +3154,15 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
return ret;
}
size_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
loff_t *ppos, int nonblocking)
ssize_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
loff_t *ppos, int nonblocking)
{
return __vb2_perform_fileio(q, data, count, ppos, nonblocking, 1);
}
EXPORT_SYMBOL_GPL(vb2_read);
size_t vb2_write(struct vb2_queue *q, const char __user *data, size_t count,
loff_t *ppos, int nonblocking)
ssize_t vb2_write(struct vb2_queue *q, const char __user *data, size_t count,
loff_t *ppos, int nonblocking)
{
return __vb2_perform_fileio(q, (char __user *) data, count,
ppos, nonblocking, 0);

8
include/media/videobuf2-core.h
View File

@@ -1093,8 +1093,8 @@ __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file,
* @ppos: file handle position tracking pointer
* @nonblock: mode selector (1 means blocking calls, 0 means nonblocking)
*/
size_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
loff_t *ppos, int nonblock);
ssize_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
loff_t *ppos, int nonblock);
/**
* vb2_write() - implements write() syscall logic.
* @q: pointer to &struct vb2_queue with videobuf2 queue.
@@ -1103,8 +1103,8 @@ size_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
* @ppos: file handle position tracking pointer
* @nonblock: mode selector (1 means blocking calls, 0 means nonblocking)
*/
size_t vb2_write(struct vb2_queue *q, const char __user *data, size_t count,
loff_t *ppos, int nonblock);
ssize_t vb2_write(struct vb2_queue *q, const char __user *data, size_t count,
loff_t *ppos, int nonblock);
/**
* typedef vb2_thread_fnc - callback function for use with vb2_thread.