Re: Duda sobre la salida de lsusb

[Camaleón <noelamac@gmail.com>]

El 2023-04-20 a las 17:23 +0200, Luis Muñoz Fuente escribió:
> 
> El 19/4/23 a las 20:57, Camaleón escribió:
> > Hum... Es el acrónimo de «ifnum» (InterfaceNumber), pero hasta ahí puedo
> > contar O:-)
> > 
> > https://docs.kernel.org/driver-api/usb/usb.html
> Ahí dice que If 0 y If 1 son distintas interfaces de una configuración de un
> dispositivo USB. No sé que significará en el caso del teclado, pero algo me
> ha aclarado. Gracias Camaleón.

USB Descriptors
https://www.beyondlogic.org/usbnutshell/usb5.shtml

USB Report Protocol
https://wiki.osdev.org/USB_Human_Interface_Devices#USB_Report_Protocol

****
The interface descriptor could be seen as a header or grouping of the 
endpoints into a functional group performing a single feature of the 
device. For example you could have a multi-function fax/scanner/printer 
device. Interface descriptor one could describe the endpoints of the 
fax function, Interface descriptor two the scanner function and 
Interface descriptor three the printer function. Unlike the 
configuration descriptor, there is no limitation as to having only one 
interface enabled at a time. A device could have 1 or many interface 
descriptors enabled at once.

Interface descriptors have a bInterfaceNumber field specifying the 
Interface number and a bAlternateSetting which allows an interface to 
change settings on the fly. For example we could have a device with two 
interfaces, interface one and interface two. Interface one has 
bInterfaceNumber set to zero indicating it is the first interface 
descriptor and a bAlternativeSetting of zero.

Interface two would have a bInterfaceNumber set to one indicating it is 
the second interface and a bAlternativeSetting of zero (default). We 
could then throw in another descriptor, also with a bInterfaceNumber 
set to one indicating it is the second interface, but this time setting 
the bAlternativeSetting to one, indicating this interface descriptor 
can be an alternative setting to that of the other interface descriptor 
two. 
***

Conforme a la explicación anterior, y trasladado a un teclado 
multimedia, se me ocurre que pueda ser útil para agrupar funciones de 
combinaciones de las teclas:

1. Sonido → subir/bajar volumen, silenciar...
2. Pantalla → brillo, conmutar con monitor externo...
3. Control multimedia → iniciar, pausar, avanzar...

Saludos,

-- 
Camaleón