On Mon, Sep 03, 2012 at 04:57:45PM +0200, Sjur Brændeland wrote: > Hi Michael, > > > How does access to descriptors work in this setup? > > When the ring is setup by remoteproc the descriptors are > also allocated using dma_alloc_coherent(). > > >> -static void free_buf(struct port_buffer *buf) > >> +/* Allcoate data buffer from DMA memory if requested */ > > > > typo > > Thanks. > > >> +static inline void * > >> +alloc_databuf(struct virtio_device *vdev, size_t size, dma_addr_t *dma_handle, > >> + gfp_t flag) > >> { > >> - kfree(buf->buf); > >> +#ifdef CONFIG_HAS_DMA > >> + if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_DMA_MEM)) { > >> + struct device *dev = &vdev->dev; > >> + /* > >> + * Allocate DMA memory from ancestors. Finding the ancestor > >> + * is a bit quirky when DMA_MEMORY_INCLUDES_CHILDREN is not > >> + * implemented. > >> + */ > >> + dev = dev->parent ? dev->parent : dev; > >> + dev = dev->parent ? dev->parent : dev; > >> + return dma_alloc_coherent(dev, size, dma_handle, flag); > >> + } > >> +#endif > > > > Are these ifdefs really needed? If DMA_MEM is set, > > can't we use dma_alloc_coherent > > unconditionally? > > If an architecture do not support DMA you will get > a link error: "unknown symbol" for dma_alloc_coherent. > > Regards, > Sjur Yes, it even seems intentional. But I have a question: can the device work without DMA? Does not VIRTIO_CONSOLE_F_DMA_MEM mean dma api is required? If yes you should just fail load. Also let's add a wrapper at top of file so ifdefs do not litter the code like this. For example: #ifdef CONFIG_HAS_DMA #define VIRTIO_CONSOLE_HAS_DMA (1) #else #define VIRTIO_CONSOLE_HAS_DMA (0) #endif Now use if instead of ifdef. -- MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization