Re: [PATCH] staging: comedi: use dma_mmap_coherent for DMA-able buffer mmap

[Dan Carpenter]

On Tue, Jun 25, 2019 at 12:26:59PM +0100, Ian Abbott wrote:
>  drivers/staging/comedi/comedi_buf.c  | 150 ++++++++++++++++++---------
>  drivers/staging/comedi/comedi_fops.c |  39 ++++---
>  2 files changed, 125 insertions(+), 64 deletions(-)
> 
> diff --git a/drivers/staging/comedi/comedi_buf.c 
> b/drivers/staging/comedi/comedi_buf.c
> index d2c8cc72a99d..3ef3ddabf139 100644
> --- a/drivers/staging/comedi/comedi_buf.c
> +++ b/drivers/staging/comedi/comedi_buf.c
> @@ -27,18 +27,19 @@ static void comedi_buf_map_kref_release(struct kref *kref)
>       unsigned int i;
>  
>       if (bm->page_list) {
> -             for (i = 0; i < bm->n_pages; i++) {
> -                     buf = &bm->page_list[i];
> -                     clear_bit(PG_reserved,
> -                               &(virt_to_page(buf->virt_addr)->flags));
> -                     if (bm->dma_dir != DMA_NONE) {
> -#ifdef CONFIG_HAS_DMA
> -                             dma_free_coherent(bm->dma_hw_dev,
> -                                               PAGE_SIZE,
> -                                               buf->virt_addr,
> -                                               buf->dma_addr);
> -#endif
> -                     } else {
> +             if (bm->dma_dir != DMA_NONE) {
> +                     /*
> +                      * DMA buffer was allocated as a single block.
> +                      * Address is in page_list[0].
> +                      */
> +                     buf = &bm->page_list[0];
> +                     dma_free_coherent(bm->dma_hw_dev,
> +                                       PAGE_SIZE * bm->n_pages,
> +                                       buf->virt_addr, buf->dma_addr);
> +             } else {
> +                     for (i = 0; i < bm->n_pages; i++) {
> +                             buf = &bm->page_list[i];
> +                             ClearPageReserved(virt_to_page(buf->virt_addr));

I think we need a NULL check here:

        if (!buf->virt_addr)
                continue;

>                               free_page((unsigned long)buf->virt_addr);
>                       }
>               }
> @@ -57,7 +58,8 @@ static void __comedi_buf_free(struct comedi_device *dev,

regards,
dan carpenter

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