Re: [PATCH 1/1] usb: gadget: f_fs: set req->num_sgs as 0 for sync io mode

[Felipe Balbi <balbi@kernel.org>]

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Hi,

Peter Chen <peter.chen@nxp.com> writes:
> The UDC core uses req->num_sgs to judge if scatter buffer list is used.
> Eg: usb_gadget_map_request_by_dev. For f_fs sync io mode, the request
> is re-used for each request, so if the 1st request->length > PAGE_SIZE,
> and the 2nd request->length is < PAGE_SIZE, the f_fs uses the 1st
> req->num_sgs for the 2nd request, it causes the UDC core get the wrong
> req->num_sgs value (The 2nd request doesn't use sg).
>
> We set req->num_sgs as 0 for each request at non-sg transfer case to
> fix it.

The patch, however, is *removing* initialization to 0...

> Cc: Jun Li <jun.li@nxp.com>
> Cc: stable <stable@vger.kernel.org>
> Fixes: 772a7a724f69 ("usb: gadget: f_fs: Allow scatter-gather buffers")
> Signed-off-by: Peter Chen <peter.chen@nxp.com>
> ---
>  drivers/usb/gadget/function/f_fs.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index eedd926cc578..b5a1bfc2fc7e 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -1106,7 +1106,6 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
>  			req->num_sgs = io_data->sgt.nents;
>  		} else {
>  			req->buf = data;
> -			req->num_sgs = 0;

... this doesn't seem to match your commit log. Care to explain?

-- 
balbi

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