From: Sebastian Siewior This got broken by the recent "fix rmmod $spi_driver while spidev-user is active". I tested the rmmod & write path but didn't check the read path. I am sorry. The read logic changed and spidev_sync_read() + spidev_sync_write() do not return zero on success anymore but the number of bytes that has been transfered over the bus. This patch changes the logic and copy_to_user() gets called again. The write path returns the number of bytes which are written to the underlying device what may be less than the requested size. This patch makes the same change to the read path or else we request a read of 20 bytes, get 10, don't call copy to user and report to the user that we read 10 bytes. Signed-off-by: Sebastian Siewior Cc: David Brownell Signed-off-by: Andrew Morton --- drivers/spi/spidev.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff -puN drivers/spi/spidev.c~spi-fix-the-read-path-in-spidev drivers/spi/spidev.c --- a/drivers/spi/spidev.c~spi-fix-the-read-path-in-spidev +++ a/drivers/spi/spidev.c @@ -167,14 +167,14 @@ spidev_read(struct file *filp, char __us mutex_lock(&spidev->buf_lock); status = spidev_sync_read(spidev, count); - if (status == 0) { + if (status > 0) { unsigned long missing; - missing = copy_to_user(buf, spidev->buffer, count); - if (count && missing == count) + missing = copy_to_user(buf, spidev->buffer, status); + if (status && missing == status) status = -EFAULT; else - status = count - missing; + status = status - missing; } mutex_unlock(&spidev->buf_lock); @@ -200,8 +200,6 @@ spidev_write(struct file *filp, const ch missing = copy_from_user(spidev->buffer, buf, count); if (missing == 0) { status = spidev_sync_write(spidev, count); - if (status == 0) - status = count; } else status = -EFAULT; mutex_unlock(&spidev->buf_lock); _