Re: [PATCH v2 6/7] gpib: fmh_gpib: Replace dma_request_slave_channel() by dma_request_chan()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] gpib: leaking -EPROBE_DEFER to userspace via ioctl
--

commit ed7181f3c8edddd4643c5d2a68386dacb851bb22
Author: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

gpib: fmh_gpib: Replace dma_request_slave_channel() by dma_request_chan()

This commit replaces the deprecated dma_request_slave_channel() with
dma_request_chan() in the fmh_gpib driver. It propagates the specific
error code returned by dma_request_chan() rather than returning a hardcoded
-EIO.

> diff --git a/drivers/gpib/fmh_gpib/fmh_gpib.c b/drivers/gpib/fmh_gpib/fmh_gpib.c
> index 5e10e9353fedd..4ab9b0a317fdb 100644
> --- a/drivers/gpib/fmh_gpib/fmh_gpib.c
> +++ b/drivers/gpib/fmh_gpib/fmh_gpib.c
> @@ -1458,11 +1458,15 @@ static int fmh_gpib_attach_impl(struct gpib_board *board, const struct gpib_boar
>  	e_priv->irq = irq;
>  
>  	if (acquire_dma) {
> -		e_priv->dma_channel = dma_request_slave_channel(board->dev, "rxtx");
> -		if (!e_priv->dma_channel) {
> +		struct dma_chan *tmp_chan;
> +
> +		tmp_chan = dma_request_chan(board->dev, "rxtx");
> +		retval = PTR_ERR_OR_ZERO(tmp_chan);
> +		if (retval) {
>  			dev_err(board->dev, "failed to acquire dma channel \"rxtx\".\n");
> -			return -EIO;
> +			return retval;

[Severity: Medium]
Could this leak -EPROBE_DEFER to userspace?

If dma_request_chan() fails due to an unavailable DMA controller, it returns
-EPROBE_DEFER. Because fmh_gpib_attach_impl() is called when a userspace
application configures the board via the IBONL ioctl:

ibioctl()
  online_ioctl()
    ibonline()
      attach()
        fmh_gpib_attach_impl()

This kernel-internal error code would be returned directly across the syscall
boundary.

Userspace applications expecting standard POSIX error codes like -EIO, -EAGAIN,
or -ENODEV might break when encountering -EPROBE_DEFER.

>  		}
> +		e_priv->dma_channel = tmp_chan;
>  	}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260918113727.1898998-1-andriy.shevchenko@linux.intel.com?part=6