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SubjectRe: [PATCH v2 2/7] drivers/soc: Add Aspeed XDMA Engine Driver


On Sat, 25 May 2019, at 01:39, Eddie James wrote:
>
> On 5/21/19 7:02 AM, Arnd Bergmann wrote:
> > On Mon, May 20, 2019 at 10:19 PM Eddie James <eajames@linux.ibm.com> wrote:
> >> diff --git a/include/uapi/linux/aspeed-xdma.h b/include/uapi/linux/aspeed-xdma.h
> >> new file mode 100644
> >> index 0000000..2a4bd13
> >> --- /dev/null
> >> +++ b/include/uapi/linux/aspeed-xdma.h
> >> @@ -0,0 +1,26 @@
> >> +/* SPDX-License-Identifier: GPL-2.0+ */
> >> +/* Copyright IBM Corp 2019 */
> >> +
> >> +#ifndef _UAPI_LINUX_ASPEED_XDMA_H_
> >> +#define _UAPI_LINUX_ASPEED_XDMA_H_
> >> +
> >> +#include <linux/types.h>
> >> +
> >> +/*
> >> + * aspeed_xdma_op
> >> + *
> >> + * upstream: boolean indicating the direction of the DMA operation; upstream
> >> + * means a transfer from the BMC to the host
> >> + *
> >> + * host_addr: the DMA address on the host side, typically configured by PCI
> >> + * subsystem
> >> + *
> >> + * len: the size of the transfer in bytes; it should be a multiple of 16 bytes
> >> + */
> >> +struct aspeed_xdma_op {
> >> + __u32 upstream;
> >> + __u64 host_addr;
> >> + __u32 len;
> >> +};
> >> +
> >> +#endif /* _UAPI_LINUX_ASPEED_XDMA_H_ */
> > If this is a user space interface, please remove the holes in the
> > data structure.
>
>
> Surely it's 4-byte aligned and there won't be holes??

__u64 is 8-byte aligned, so you have a hole after upstream.

Easiest just to put upstream after len?

Andrew

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