Hello Laurent, thanks for the feedback and apologies for the delayed reply. On Sun, 11 Dec 2022 18:55:39 +0200 Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > Hi Tomi and Luca, > > Thank you for the patch. > > On Thu, Dec 08, 2022 at 12:39:59PM +0200, Tomi Valkeinen wrote: > > From: Luca Ceresoli <luca@xxxxxxxxxxxxxxxx> > > > > An adapter might need to know when a new device is about to be > > added. This will soon bee needed to implement an "I2C address > > translator" (ATR for short), a device that propagates I2C transactions > > with a different slave address (an "alias" address). An ATR driver > > needs to know when a slave is being added to find a suitable alias and > > program the device translation map. > > > > Add an attach/detach callback pair to allow adapter drivers to be > > notified of clients being added and removed. > > This may be a stupid question, but couldn't you instead use the > BUS_NOTIFY_ADD_DEVICE and BUS_NOTIFY_DEL_DEVICE bus notifiers ? I'm not sure they would be the correct tool for this task. Bus notifiers inform about new events on the 'struct bus_type, i.e. any event on the global i2c bus type. In the i2c world this means being notified about new _adapters_, which is exactly what drivers/i2c/i2c-dev.c does. Here, however, we need to be informed about new _clients_ being added under a specific adapter. I'm not sure whether the bus notifiers can inform about new clients in addition of new adapters, but they at least seem unable to provide per-adapter notification. Does that seem correct? Best regards, -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
