On Wednesday 17 December 2014 13:02:23 Murali Karicheri wrote:
> Now, in Kernel, parent device's DMA parameters has to be applied to
> the child as is - to enable DMA support for the device. Usually this
> is happened in places where parent device manually instantiates child
> device such as in drivers/pci/probe.c (pci_device_add() for example).
>
> Now DMA configuration is represented in device data structure not only
> by DMA mask and DMA params, it also includes dma_pfn_offset at least.
> Hence introduce common dma_get_parent_cfg() helper to apply dma
> configuration from parent to child, and use __weak to allow arch to
> override it if needed.
>
> Signed-off-by: Murali Karicheri <m-karicheri2@xxxxxx>
> ---
> drivers/base/dma-mapping.c | 18 ++++++++++++++++++
> include/linux/dma-mapping.h | 3 +++
> 2 files changed, 21 insertions(+)
>
> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
> index 9e8bbdd..5322426 100644
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
> @@ -339,3 +339,21 @@ void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
> vunmap(cpu_addr);
> }
> #endif
> +
> +int __weak dma_get_parent_cfg(struct device *dev, struct device *parent)
> +{
> + struct device *temp = parent;
> +
> + if (!temp)
> + temp = dev->parent;
> +
> + if (temp && is_device_dma_capable(temp)) {
> + dev->dma_mask = temp->dma_mask;
> + dev->coherent_dma_mask = temp->coherent_dma_mask;
As discussed, setting the pointers like this is always wrong,
so don't do it.
What's wrong with using arch_setup_dma_ops() from PCI as suggested
previously?
Arnd
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