Messages in this thread | | | Date | Mon, 3 Sep 2012 16:57:45 +0200 | Subject | Re: [RFC 1/2] virtio_console: Add support for DMA memory allocation | From | Sjur Brændeland <> |
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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
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