Hi Jack-san,
> -----Original Message-----
> From: Jack Pham
> Sent: Tuesday, August 1, 2017 6:01 PM
> Subject: [PATCH] usb: gadget: core: unmap request from DMA only if previously
> mapped
>
> In the SG case this is already handled since a non-zero
> request->num_mapped_sgs is a clear indicator that dma_map_sg()
> had been called. While it would be nice to do the same for the
> singly mapped case by simply checking for non-zero request->dma,
> it's conceivable that 0 is a valid dma_addr_t handle. Hence add
> a flag 'dma_mapped' to struct usb_request and use this to
> determine the need to call dma_unmap_single(). Otherwise, if a
> request is not DMA mapped then the result of calling
> usb_request_unmap_request() would safely be a no-op.
>
> Signed-off-by: Jack Pham <ja...@codeaurora.org>
> ---
> Hi Felipe,
>
> Here's what I came up with after our discussion back in [1]. It
> turned out to be pretty dead-simple and hopefully doesn't need to
> approach the number of URB flags that the host core uses.
>
> I did a quick survey of all callers of usb_gadget_{map,unmap}_request
> and besides the instance I reported & patched in dwc3, from what I
> can tell it looks like all the other gadget drivers seem to be calling
> these APIs sanely--i.e. a request is only queued after being
> successfully mapped, and unmap only ever gets called on requests that
> had been queued.
>
> Although in one instance (renesas_usb3.c), there is a 'used' flag as
> part of struct renesas_usb3_dma that looks like it's tracking the
> status of whether a request is mapped or not, but it's not obvious from
> cursory glance whether it has a use besides that or if it would be
> sufficient to just rely on this new flag in struct usb_gadget.
> Maybe Yoshihiro-san can comment.
About the 'used' flag on renesas_usb3.c, I don't think the driver is able to
rely on this new flag 'dma_mapped' in struct usb_request because the 'used' flag
will be used for marking the dma channels.
This controller only handles 4 channels(endpoints) at the same time.
So, this driver has 'used' in struct renesas_usb3_dma.
But, I think this patch is good to unmap safety.
So,
Acked-by: Yoshihiro Shimoda <yoshihiro.shimoda...@renesas.com>
Best regards,
Yoshihiro Shimoda
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