Messages in this thread | | | Subject | Re: [PATCH] staging: comedi: s626: Remove pci-dma-compat wrapper APIs. | From | Ian Abbott <> | Date | Mon, 13 Jul 2020 14:48:41 +0100 |
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On 11/07/2020 14:38, Christophe JAILLET wrote: > Le 11/07/2020 à 14:35, Suraj Upadhyay a écrit : >> The legacy API wrappers in include/linux/pci-dma-compat.h >> should go away as it creates unnecessary midlayering >> for include/linux/dma-mapping.h APIs, instead use dma-mapping.h >> APIs directly. >> >> The patch has been generated with the coccinelle script below >> and compile-tested. >> >> [...] >> @@ expression E1, E2, E3; @@ >> - pci_alloc_consistent(E1, E2, E3) >> + dma_alloc_coherent(&E1->dev, E2, E3, GFP_ATOMIC) >> >> @@ expression E1, E2, E3; @@ >> - pci_zalloc_consistent(E1, E2, E3) >> + dma_alloc_coherent(&E1->dev, E2, E3, GFP_ATOMIC) > > This is the tricky part of this kind of cleanup, see below. > > GFP_ATOMIC can't be wrong because it is was exactly what was done with > the pci_ function. > However, most of the time, it can safely be replaced by GFP_KERNEL which > gives more opportunities to the memory allocator. > >> [...] >> diff --git a/drivers/staging/comedi/drivers/s626.c >> b/drivers/staging/comedi/drivers/s626.c >> index 084a8e7b9fc2..c159416662fd 100644 >> --- a/drivers/staging/comedi/drivers/s626.c >> +++ b/drivers/staging/comedi/drivers/s626.c >> @@ -2130,13 +2130,15 @@ static int s626_allocate_dma_buffers(struct >> comedi_device *dev) >> void *addr; >> dma_addr_t appdma; >> - addr = pci_alloc_consistent(pcidev, S626_DMABUF_SIZE, &appdma); >> + addr = dma_alloc_coherent(&pcidev->dev, S626_DMABUF_SIZE, &appdma, >> + GFP_ATOMIC); >> if (!addr) >> return -ENOMEM; >> devpriv->ana_buf.logical_base = addr; >> devpriv->ana_buf.physical_base = appdma; >> - addr = pci_alloc_consistent(pcidev, S626_DMABUF_SIZE, &appdma); >> + addr = dma_alloc_coherent(&pcidev->dev, S626_DMABUF_SIZE, &appdma, >> + GFP_ATOMIC); >> if (!addr) >> return -ENOMEM; >> devpriv->rps_buf.logical_base = addr; > 's626_allocate_dma_buffers()' is only called from 's626_auto_attach()'. > In this function, around the call to 's626_allocate_dma_buffers()', you > can see: > - a few lines before, a call to 'comedi_alloc_devpriv()' > > - a few lines after, a call to 'comedi_alloc_subdevices()' > > These 2 functions make some memory allocation using GFP_KERNEL. > > So it is likely that using GFP_KERNEL in your proposal is also valid.
Indeed, GFP_KERNEL is perfectly fine here. It could be done as a follow-up patch, or done in a v2 of this patch with a mention in the patch description.
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