Re: [PATCH/RFC 4/6] mm: Add NO_DMA dummies for DMA pool API

[Robin Murphy <robin.murphy@xxxxxxx>]

Hi Geert,

On 06/02/18 10:14, Geert Uytterhoeven wrote:
> Add dummies for dma{,m}_pool_{create,destroy,alloc,free}(), to allow
> compile-testing if NO_DMA=y.
>
> This prevents the following from showing up later:
>
>      ERROR: "dma_pool_destroy" [drivers/usb/mtu3/mtu3.ko] undefined!
>      ERROR: "dma_pool_free" [drivers/usb/mtu3/mtu3.ko] undefined!
>      ERROR: "dma_pool_alloc" [drivers/usb/mtu3/mtu3.ko] undefined!
>      ERROR: "dma_pool_create" [drivers/usb/mtu3/mtu3.ko] undefined!
>      ERROR: "dma_pool_destroy" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!
>      ERROR: "dma_pool_free" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!
>      ERROR: "dma_pool_alloc" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!
>      ERROR: "dma_pool_create" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!
>      ERROR: "dma_pool_alloc" [drivers/mailbox/bcm-pdc-mailbox.ko] undefined!
>      ERROR: "dma_pool_free" [drivers/mailbox/bcm-pdc-mailbox.ko] undefined!
>      ERROR: "dma_pool_create" [drivers/mailbox/bcm-pdc-mailbox.ko] undefined!
>      ERROR: "dma_pool_destroy" [drivers/mailbox/bcm-pdc-mailbox.ko] undefined!
>
> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> ---
>   include/linux/dmapool.h | 21 +++++++++++++++++++--
>   1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/dmapool.h b/include/linux/dmapool.h
> index 53ba737505df31c7..adeb5e56c3ad73a8 100644
> --- a/include/linux/dmapool.h
> +++ b/include/linux/dmapool.h
> @@ -16,6 +16,7 @@
>   
>   struct device;
>   
> +#ifdef CONFIG_HAS_DMA
>   struct dma_pool *dma_pool_create(const char *name, struct device *dev,
>   			size_t size, size_t align, size_t allocation);
>   
> @@ -23,6 +24,17 @@ void dma_pool_destroy(struct dma_pool *pool);
>   
>   void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
>   		     dma_addr_t *handle);
> +void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t addr);
> +#else /* !CONFIG_HAS_DMA */
> +static inline struct dma_pool *dma_pool_create(const char *name,
> +	struct device *dev, size_t size, size_t align, size_t allocation)
> +{ return NULL; }
> +static inline void dma_pool_destroy(struct dma_pool *pool) { }
> +static inline void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
> +				   dma_addr_t *handle) { return NULL; }
> +static inline void dma_pool_free(struct dma_pool *pool, void *vaddr,
> +				 dma_addr_t addr) { }
> +#endif /* !CONFIG_HAS_DMA */
>   
>   static inline void *dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
>   				    dma_addr_t *handle)
> @@ -30,14 +42,19 @@ static inline void *dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
>   	return dma_pool_alloc(pool, mem_flags | __GFP_ZERO, handle);
>   }
>   
> -void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t addr);
> -
>   /*
>    * Managed DMA pool
>    */
> +#ifdef CONFIG_HAS_DMA
>   struct dma_pool *dmam_pool_create(const char *name, struct device *dev,
>   				  size_t size, size_t align, size_t allocation);
>   void dmam_pool_destroy(struct dma_pool *pool);
> +#else /* !CONFIG_HAS_DMA */
> +static inline struct dma_pool *dmam_pool_create(const char *name,
> +	struct device *dev, size_t size, size_t align, size_t allocation)
> +{ return NULL; }
> +static inline void dmam_pool_destroy(struct dma_pool *pool) { }
> +#endif /* !CONFIG_HAS_DMA */

Nit: It might be tidier to add *all* the stubs down here so that there 
only need be a single #ifdef, then move the dma_pool_zalloc definition 
outside at the end (where we might eventually get rid of it anyway).

Other than that, though, I think I agree with the series in general - 
more COMPILE_TEST is always good from the point of view of weeding out 
drivers using architecture-specific DMA API internals which aren't part 
of the proper generic interface.

Robin.

>   
>   #endif
>