Re: [PATCH 1/2] uio: introduce UIO_MEM_DMA_COHERENT type

[Thomas Weißschuh]

Hi,

On Wed, Jan 31, 2024 at 11:17:31AM -0800, Chris Leech wrote:
> Add a UIO memtype specifically for sharing dma_alloc_coherent
> memory with userspace, backed by dma_mmap_coherent.
> 
> This is mainly for the bnx2/bnx2x/bnx2i "cnic" interface, although there
> are a few other uio drivers which map dma_alloc_coherent memory and
> could be converted to use dma_mmap_coherent as well.
> 
> Signed-off-by: Nilesh Javali <njavali@xxxxxxxxxxx>
> Signed-off-by: Chris Leech <cleech@xxxxxxxxxx>
> ---
>  drivers/uio/uio.c          | 40 ++++++++++++++++++++++++++++++++++++++
>  include/linux/uio_driver.h |  3 +++
>  2 files changed, 43 insertions(+)
> 
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index 2d572f6c8ec83..dde3f49855233 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
> @@ -24,6 +24,7 @@

[..]

> +static int uio_mmap_dma_coherent(struct vm_area_struct *vma)
> +{
> +	struct uio_device *idev = vma->vm_private_data;
> +	struct uio_mem *mem;
> +	void *addr;
> +	int ret = 0;
> +	int mi;
> +
> +	mi = uio_find_mem_index(vma);
> +	if (mi < 0)
> +		return -EINVAL;
> +
> +	mem = idev->info->mem + mi;
> +
> +	if (mem->dma_addr & ~PAGE_MASK)
> +		return -ENODEV;
> +	if (vma->vm_end - vma->vm_start > mem->size)
> +		return -EINVAL;
> +
> +	/*
> +	 * UIO uses offset to index into the maps for a device.
> +	 * We need to clear vm_pgoff for dma_mmap_coherent.
> +	 */
> +	vma->vm_pgoff = 0;
> +
> +	addr = (void *)mem->addr;

This cast introduces a build error when building with
sizeof(void *) != sizeof(phys_addr_t).

For example on i386 with PHYS_ADDR_T_64BIT.
(Enabled through allmodconfig)

drivers/uio/uio.c: In function 'uio_mmap_dma_coherent':
drivers/uio/uio.c:795:16: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  795 |         addr = (void *)mem->addr;
      |                ^
drivers/uio/uio_pruss.c: In function 'pruss_probe':
drivers/uio/uio_pruss.c:194:34: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
  194 |                 p->mem[2].addr = (phys_addr_t) gdev->ddr_vaddr;
      |                                  ^
drivers/uio/uio_dmem_genirq.c: In function 'uio_dmem_genirq_open':
drivers/uio/uio_dmem_genirq.c:63:39: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
   63 |                 uiomem->addr = addr ? (phys_addr_t) addr : DMEM_MAP_ERROR;
      |                                       ^
drivers/uio/uio_dmem_genirq.c: In function 'uio_dmem_genirq_release':
drivers/uio/uio_dmem_genirq.c:92:43: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
   92 |                                           (void *) uiomem->addr,

As you can see some other files are also affected, which seem to be
triggered by other but related patches.

This is on next-20240312.

> +	ret = dma_mmap_coherent(mem->dma_device,
> +				vma,
> +				addr,
> +				mem->dma_addr,
> +				vma->vm_end - vma->vm_start);
> +	vma->vm_pgoff = mi;
> +
> +	return ret;
> +}
> +

[..]

Thomas