On Wed, Jan 13, 2021 at 8:42 PM Christoph Hellwig <hch@xxxxxx> wrote:
>
> > +#ifdef CONFIG_SWIOTLB
> > + struct io_tlb_mem *dma_io_tlb_mem;
> > #endif
>
> Please add a new config option for this code instead of always building
> it when swiotlb is enabled.
>
> > +static int swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
> > + size_t size)
>
> Can you split the refactoring in swiotlb.c into one or more prep
> patches?
>
> > +static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
> > + struct device *dev)
> > +{
> > + struct io_tlb_mem *mem = rmem->priv;
> > + int ret;
> > +
> > + if (dev->dma_io_tlb_mem)
> > + return -EBUSY;
> > +
> > + if (!mem) {
> > + mem = kzalloc(sizeof(*mem), GFP_KERNEL);
> > + if (!mem)
> > + return -ENOMEM;
>
> What is the calling convention here that allows for a NULL and non-NULL
> private data?
Since multiple devices can share the same pool, the private data,
io_tlb_mem struct, will be initialized by the first device attached to
it.
This is similar to rmem_dma_device_init() in kernel/dma/coherent.c.
I'll add a comment for it in next version.
