On Mon, 2019-02-18 at 12:37 +0300, Dan Carpenter wrote: > 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 <[email protected]> > > > > > > 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 <[email protected]> > > > --- > > > 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; > > (Probably they broke it up into two shifts to silence a GCC warning > that the shift was wrong because of the missing cast?)
No because dma_addr_t can be 32 bits and the warning would then always appear on some builds. The << 16 << 16 makes sure it doesn't. James
