> Peter Chen <peter.chen@xxxxxxx> 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@xxxxxxx>
> > Cc: stable <stable@xxxxxxxxxxxxxxx>
> > Fixes: 772a7a724f69 ("usb: gadget: f_fs: Allow scatter-gather
> > buffers")
> > Signed-off-by: Peter Chen <peter.chen@xxxxxxx>
> > ---
> > 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?
>
Sorry, I did not check the patch when I formatted it. I need to pay more attention to it next time.
I will send it again.
Peter
