Messages in this thread | | | Subject | Re: [PATCH] staging: comedi: s626: Remove pci-dma-compat wrapper APIs. | From | Christophe JAILLET <> | Date | Sat, 11 Jul 2020 15:38:37 +0200 |
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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.
Just my 2c.
CJ
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