Messages in this thread | | | From | Zheyu Ma <> | Date | Thu, 26 May 2022 20:02:28 +0800 | Subject | Re: [PATCH v2] char: xillybus: Check endpoint type before allocing |
| |
On Tue, May 24, 2022 at 8:24 PM Eli Billauer <eli.billauer@gmail.com> wrote: > > On 23/05/22 20:15, Greg KH wrote: > >> Rather, it works like this: The driver uses the EP 1 IN and OUT endpoints to > >> > query the device for a data structure, which contains information on the > >> > device's communication channels. The driver sets up device files > >> > accordingly, and it also gets informed on which bulk OUT endpoints are > >> > present. > >> > > >> > For what it's worth, I think it's fairly safe to assume that if a device > >> > returns a legal data structure (which passes a CRC test), it's a XillyUSB > >> > device. > >> > > Why? You still need to verify that the requested endpoints match up > > with what the device really has. > > > OK. So to summarize: > > EP 1 IN and EP 1 OUT are always present in XillyUSB devices. > > On top of these, there might be additional bulk OUT endpoints. The > driver resolves which ones in setup_channels(), by scanning a data blob > it has received from the device. This takes place in the for-loop inside > this function. When (out_desc & 0x80) is true for a given @i in the > loop, the device has a bulk OUT endpoint with address i+2 (e.g. if this > condition is met for i==2, the device has a bulk OUT EP 4). > > So it seems like setup_channels() would be the right place to make this > check, since it's called during the device's probe. > > I guess it would likewise make sense to check for EP 1 IN and OUT in > xillyusb_setup_base_eps(). > > Thanks, > Eli
Thanks for the detailed explanation, I will try to send a new version of the patch to fix the bug.
Thanks, Zheyu Ma
| |