> -----Original Message----- > From: Jiri Kosina [mailto:jkosina@xxxxxxx] > Sent: Monday, May 12, 2014 2:27 PM > To: Benjamin Tissoires > Cc: Archana Patni; jic23@xxxxxxxxxx; linux-input; Westerberg, Mika; > Pandruvada, Srinivas; Patni, Archana; Sesha, Subramony > Subject: Re: [PATCH] HID: i2c-hid: hid report descriptor retrieval changes > > On Thu, 8 May 2014, Benjamin Tissoires wrote: > > > > Reading the partial HID Descriptor is causing a firmware lockup in > > > some sensor hubs. Instead of a partial read, this patch implements > > > the i2c hid fetch using a fixed descriptor size (30 bytes) followed > > > by a verification of the BCDVersion (V01.00), and value stored in > > > wHIDDescLength (30 Bytes) for V1.00 descriptors. > > > > > > As per i2c hid spec, this is the preferred model. > > > > > > From hid-over-i2c-protocol-spec-v1-0: > > > > > > There are a variety of ways a HOST may choose to retrieve > > > the HID Descriptor from the DEVICE. The following is a preferred > > > implementation but should not be considered the only implementation. > > > A HOST may read the entire HID Descriptor in a single read by > > > issuing a read for 30 Bytes to get the entire HID Descriptor > > > from the DEVICE.However, the HOST is responsible for validating > > > that > > > > > > 1. The BCDVersion is V01.00 (later revisions may have different > > > descriptor lengths), and > > > > > > 2. The value stored in wHIDDescLength is 30 (Bytes) for V1.00 > > > descriptors. > > > > > > Reported-by: Joe Tijerina <joe.tijerina@xxxxxx> > > > Signed-off-by: Archana Patni <archana.patni@xxxxxxxxx> > > > Signed-off-by: Subramony Sesha <subramony.sesha@xxxxxxxxx> > > > Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > > > --- > > > > This one is Reviewed-by: Benjamin Tissoires > > <benjamin.tissoires@xxxxxxxxxx> > > Do we have any indication about how frequently are the lockups actually > happening in the wild? Is this a regression? (I don't think so). For a few devices, this behavior always occurs. This is not a regression. > > The reason I am asking is whether I should rush this in for 3.15 still, but as the > patch doesn't have stable annotation anyway, my understanding is that 3.16 > is enough? 3.16 is fine. Thanks Archana > > Thanks, > > -- > Jiri Kosina > SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
