Am 18.02.2019 10:37, schrieb Dan Carpenter:
> On Sat, Feb 16, 2019 at 05:27:16PM +0100, Walter Harms wrote:
>> Am 16.02.2019 15:44, schrieb Colin King:
>>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>>
>>> Currently m_sg->baseaddr_h (a 32 bit unsigned int) is being shifted by a
>>> total of 32 bits; this always produces a 0 result. Fix this by casting
>>> it to a dma_addr_t (a 64 bit unsigned int) before performing the shift.
>>>
>>> Detected by CoverityScan, CID#147270 ("Operands don't affect result")
>>>
>>> Fixes: f0c568a478f0 ("[SCSI] mvumi: Add Marvell UMI driver")
>>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>> ---
>>> drivers/scsi/mvumi.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/scsi/mvumi.c b/drivers/scsi/mvumi.c
>>> index 36f64205ecfa..d3582accfd09 100644
>>> --- a/drivers/scsi/mvumi.c
>>> +++ b/drivers/scsi/mvumi.c
>>> @@ -313,7 +313,7 @@ static void mvumi_delete_internal_cmd(struct mvumi_hba
>>> *mhba,
>>> sgd_getsz(mhba, m_sg, size);
>>>
>>> phy_addr = (dma_addr_t) m_sg->baseaddr_l |
>>> - (dma_addr_t) ((m_sg->baseaddr_h << 16) << 16);
>>> + (((dma_addr_t) m_sg->baseaddr_h << 16) << 16);
>>>
>>> dma_free_coherent(&mhba->pdev->dev, size, cmd->data_buf,
>>> phy_addr);
>>
>> i would suggest to try a version with less casts to make it more readable
>> like this untested suggestion:
>>
>> phy_addr =(m_sg->baseaddr_h << 16)| m_sg->baseaddr_l;
>> phy_addr <<= 16;
>>
>
> That would be a behavior change but it also might be a bugfix? Why
> doesn't the code just do:
>
> phy_addr = ((dma_addr_t)m_sg->baseaddr_h << 32) | m_sg->baseaddr_l;
>
phy_addr = ((dma_addr_t)m_sg->baseaddr_h << 32) | m_sg->baseaddr_l<<16;
The question is how to solv propperly this without confusing the future reader.
Lets wait what opinion the maintainer has.
re,
wh
> (Probably they broke it up into two shifts to silence a GCC warning that
> the shift was wrong because of the missing cast?)
>
> regards,
> dan carpenter
>
>
>
