[PATCH v3 0/6] Generic USB Display driver

[Noralf Trønnes]

Den 14.07.2020 19.40, skrev Peter Stuge:
> Hi Noralf,
> 
> Noralf Trønnes wrote:
>> I would like to keep the SET_BUFFER request since it will serve as a
>> syncing point between the host and the device. I'm no USB expert but I
>> assume that a bulk transfer can fail halfway through and result in the
>> next update starting where the previous one failed and thus writing
>> beyond the end of the display buffer.
> 
> Transfers either succeed completely (possibly after many retries),
> time out (after zero or more transfered bytes) or fail catastrophically
> (e.g. from device disconnect).
> 
> In all cases, the driver on the host knows/has available how many bytes
> were successfully transfered.
> 

I was thinking about the device, that it could get out of sync. Let's
say the host sends a 1k framebuffer and half of it gets transferred and
the rest fails for some reason. Lubomir's MCU implementation has an
endpoint max size of 64 bytes and a callback is called for each packet.
If the 1k transfer fails at some point, will the device be able to
detect this and know that the next time the rx callback is called that
this is the start of a new framebuffer update?

Noralf.