linux-kernel - Re: [PATCH][drivers/scsi/u14-34f.c] duplicate test 'SCpnt->sc_data_direction == DMA_FROM

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Date:	Wed, 06 Feb 2008 11:45:39 -0600
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Roel Kluin <12o3l@...cali.nl>
Cc:	ballabio_dario@....com, linux-scsi@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][drivers/scsi/u14-34f.c] duplicate test
	'SCpnt->sc_data_direction == DMA_FROM_DEVICE'


On Mon, 2008-02-04 at 23:36 +0100, Roel Kluin wrote:
> It should be like this I guess? this patch was not yet tested, please
> confirm.
> --
> Note the duplicate test 'SCpnt->sc_data_direction == DMA_FROM_DEVICE'
> 
> from Documentation/DMA-API.txt:
> DMA_TO_DEVICE         = PCI_DMA_TODEVICE      data is going from the
>                                               memory to the device
> DMA_FROM_DEVICE       = PCI_DMA_FROMDEVICE    data is coming from
>                                               the device to the
> 
> Signed-off-by: Roel Kluin <12o3l@...cali.nl>
> ---
> diff --git a/drivers/scsi/u14-34f.c b/drivers/scsi/u14-34f.c
> index 662c004..1e704f9 100644
> --- a/drivers/scsi/u14-34f.c
> +++ b/drivers/scsi/u14-34f.c
> @@ -1208,15 +1208,15 @@ static void scsi_to_dev_dir(unsigned int i, unsigned int j) {
>        };
>  
>     struct mscp *cpp;
>     struct scsi_cmnd *SCpnt;
>  
>     cpp = &HD(j)->cp[i]; SCpnt = cpp->SCpnt;
>  
> -   if (SCpnt->sc_data_direction == DMA_FROM_DEVICE) {
> +   if (SCpnt->sc_data_direction == DMA_TO_DEVICE) {
>        cpp->xdir = DTD_IN;
>        return;
>        }
>     else if (SCpnt->sc_data_direction == DMA_FROM_DEVICE) {
>        cpp->xdir = DTD_OUT;
>        return;
>        }

Well spotted, this is definitely a huge bug in the driver.

However, I think on closer examination that DTD_IN actually means
transfer from device to host, so DMA_FROM_DEVICE is correct for that
case.  It should be DMA_TO_DEVICE in the else if() piece.

Could you correct and resend the patch and I'll apply it.

Thanks,

James


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