On Thu, 30 Jan 2025 11:59:05 +0100,
John Keeping wrote:
>
> On Thu, Jan 30, 2025 at 11:50:07AM +0100, Takashi Iwai wrote:
> > On Wed, 29 Jan 2025 18:31:35 +0100,
> > John Keeping wrote:
> > >
> > > On Wed, Jan 29, 2025 at 05:40:04PM +0100, Takashi Iwai wrote:
> > > > On Wed, 29 Jan 2025 17:05:19 +0100,
> > > > John Keeping wrote:
> > > > >
> > > > > In the two loops before setting the MIDIStreaming descriptors,
> > > > > ms_in_desc.baAssocJackID[] has entries written for "in_ports" values and
> > > > > ms_out_desc.baAssocJackID[] has entries written for "out_ports" values.
> > > > > But the counts and lengths are set the other way round in the
> > > > > descriptors.
> > > > >
> > > > > Fix the descriptors so that the bNumEmbMIDIJack values and the
> > > > > descriptor lengths match the number of entries populated in the trailing
> > > > > arrays.
> > > >
> > > > Are you sure that it's a correct change?
> > > >
> > > > IIUC, the in_ports and out_ports parameters are for external IN and
> > > > OUT jacks, where an external OUT jack is connected to an embedded IN
> > > > jack, and an external IN jack is connected to an embedded OUT jack.
> > >
> > > I think it depends how the in_ports and out_ports values in configfs are
> > > interpreted. However, the case where in_ports != out_ports has been
> > > broken since these files were added!
> > >
> > > Without this change, setting in_ports=4 out_ports=2 we end up with:
> > >
> > > Endpoint Descriptor:
> > > [...]
> > > bEndpointAddress 0x01 EP 1 OUT
> > > [...]
> > > MIDIStreaming Endpoint Descriptor:
> > > bLength 8
> > > bDescriptorType 37
> > > bDescriptorSubtype 1 (Invalid)
> > > bNumEmbMIDIJack 4
> > > baAssocJackID( 0) 9
> > > baAssocJackID( 1) 11
> > > baAssocJackID( 2) 9
> > > baAssocJackID( 3) 0
> > > Endpoint Descriptor:
> > > [...]
> > > bEndpointAddress 0x81 EP 1 IN
> > > [...]
> > > MIDIStreaming Endpoint Descriptor:
> > > bLength 6
> > > bDescriptorType 37
> > > bDescriptorSubtype 1 (Invalid)
> > > bNumEmbMIDIJack 2
> > > baAssocJackID( 0) 2
> > > baAssocJackID( 1) 4
> > >
> > > Note that baAssocJackID values 2 and 3 on the OUT endpoint are wrong.
> > >
> > > From the same config, the jack definitions are:
> > >
> > > 1: IN External
> > > 2: OUT Embedded, source 1
> > > 3: IN External
> > > 4: OUT Embedded, source 3
> > > 5: IN External
> > > 6: OUT Embedded, source 5
> > > 7: IN External
> > > 8: OUT Embedded, source 7
> > >
> > > 9: IN Embedded
> > > 10: OUT External, source 9
> > > 11: IN Embedded
> > > 12: OUT External, source 11
> > >
> > > So it seems that the first 2 entries in each endpoint list are correct.
> > > For the OUT endpoint, jacks 9 and 11 are embedded IN jacks and for the
> > > IN endpoint, jacks 2 and 4 are embedded OUT jacks.
> > >
> > > The problem is that the OUT endpoint lists two extra invalid jack IDs
> > > and the IN endpoint should list jacks 6 and 8 but does not.
> > >
> > > After applying this patch, the endpoint descriptors for the same config
> > > are:
> > >
> > > Endpoint Descriptor:
> > > [...]
> > > bEndpointAddress 0x01 EP 1 OUT
> > > [...]
> > > MIDIStreaming Endpoint Descriptor:
> > > bLength 6
> > > bDescriptorType 37
> > > bDescriptorSubtype 1 (Invalid)
> > > bNumEmbMIDIJack 2
> > > baAssocJackID( 0) 9
> > > baAssocJackID( 1) 11
> > > Endpoint Descriptor:
> > > [...]
> > > bEndpointAddress 0x81 EP 1 IN
> > > [...]
> > > MIDIStreaming Endpoint Descriptor:
> > > bLength 8
> > > bDescriptorType 37
> > > bDescriptorSubtype 1 (Invalid)
> > > bNumEmbMIDIJack 4
> > > baAssocJackID( 0) 2
> > > baAssocJackID( 1) 4
> > > baAssocJackID( 2) 6
> > > baAssocJackID( 3) 8
> > >
> > > Which lists all the jack IDs where they should be.
> >
> > Hmm, I don't get your point. The embedded IN is paired with the
> > external OUT. That's the intended behavior, no?
>
> Yes, all the endpoint assignments are correct - when they appear in the
> lists!
>
> The issue is setting bNumEmbMIDIJack and bLength in the MIDIStreaming
> Endpoint Descriptors. Without this patch these are set the wrong way
> round so either some ports do not appear or there are bogus entries
> containing uninitialized stack memory.
OK, now point taken. The main problem here is the definition of
in_port and out_ports aren't really clear. If in_ports really
corresponds to external IN jacks, then we may correct rather like:
--- a/drivers/usb/gadget/function/f_midi.c
+++ b/drivers/usb/gadget/function/f_midi.c
@@ -968,7 +968,7 @@ static int f_midi_bind(struct usb_configuration *c, struct usb_function *f)
midi_function[i++] = (struct usb_descriptor_header *) out_emb;
/* link it to the endpoint */
- ms_in_desc.baAssocJackID[n] = out_emb->bJackID;
+ ms_out_desc.baAssocJackID[n] = out_emb->bJackID;
}
/* configure the external OUT jacks, each linked to an embedded IN jack */
@@ -996,7 +996,7 @@ static int f_midi_bind(struct usb_configuration *c, struct usb_function *f)
midi_function[i++] = (struct usb_descriptor_header *) out_ext;
/* link it to the endpoint */
- ms_out_desc.baAssocJackID[n] = in_emb->bJackID;
+ ms_in_desc.baAssocJackID[n] = in_emb->bJackID;
}
/* configure the endpoint descriptors ... */
OTOH, the current code will make the actual appearance other way
round, likely more confusing. So I believe your fix makes sense.
But it'd be helpful to extend the description a bit more to clarify
this confusion. I guess this confusion came from the association
between the embedded and external jacks, and the patch corrects it.
thanks,
Takashi
>
>
>
> Regards,
> John
>
> > > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > > Fixes: c8933c3f79568 ("USB: gadget: f_midi: allow a dynamic number of input and output ports")
> > > > > Signed-off-by: John Keeping <jkeeping@xxxxxxxxxxxxxxxxx>
> > > > > ---
> > > > > drivers/usb/gadget/function/f_midi.c | 8 ++++----
> > > > > 1 file changed, 4 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
> > > > > index 837fcdfa3840f..6cc3d86cb4774 100644
> > > > > --- a/drivers/usb/gadget/function/f_midi.c
> > > > > +++ b/drivers/usb/gadget/function/f_midi.c
> > > > > @@ -1000,11 +1000,11 @@ static int f_midi_bind(struct usb_configuration *c, struct usb_function *f)
> > > > > }
> > > > >
> > > > > /* configure the endpoint descriptors ... */
> > > > > - ms_out_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->in_ports);
> > > > > - ms_out_desc.bNumEmbMIDIJack = midi->in_ports;
> > > > > + ms_out_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->out_ports);
> > > > > + ms_out_desc.bNumEmbMIDIJack = midi->out_ports;
> > > > >
> > > > > - ms_in_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->out_ports);
> > > > > - ms_in_desc.bNumEmbMIDIJack = midi->out_ports;
> > > > > + ms_in_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->in_ports);
> > > > > + ms_in_desc.bNumEmbMIDIJack = midi->in_ports;
> > > > >
> > > > > /* ... and add them to the list */
> > > > > endpoint_descriptor_index = i;
> > > > > --
> > > > > 2.48.1
> > > > >
> > > > >
