Em 05-01-2011 19:51, Jean Delvare escreveu: > Hi Mauro, > > On Wed, 05 Jan 2011 15:34:28 -0200, Mauro Carvalho Chehab wrote: >> Hi Jean, >> >> Thanks for your acks for patches 1 and 2. I've already applied the patches >> on my tree and at linux-next. I'll try to add the acks on it before sending >> upstream. > > If you can't, it's fine. I merely wanted to show my support to Andy's > work, I don't care if I'm not counted as a reviewer for these small > patches. Ok. So, it is probably better to keep it as-is, to avoid rebasing and having to wait for a couple days at linux-next before sending the git pull request. > >> Em 05-01-2011 12:45, Jean Delvare escreveu: >>> From a purely technical perspective, changing client->addr in the >>> probe() function is totally prohibited. >> >> Agreed. Btw, there are some other hacks with client->addr abuse on some >> other random places at drivers/media, mostly at the device bridge code, >> used to test if certain devices are present and/or to open some I2C gates >> before doing some init code. People use this approach as it provides a >> fast way to do some things. On several cases, the amount of code for >> doing such hack is very small, when compared to writing a new I2C driver >> just to do some static initialization code. Not sure what would be the >> better approach to fix them. > > Hard to tell without seeing the exact code. Ideally, > i2c_new_dummy() would cover these cases: you don't need to write an > actual driver for the device, it's perfectly OK to use the freshly > instantiated i2c_client from the bridge driver directly. Alternatively, > i2c_smbus_xfer() or i2c_transfer() can be used for one-time data > exchange with any slave on the bus as long as you know what you're > doing (i.e. you know that no i2c_client will ever be instantiated for > this slave.) > > If you have specific cases you don't know how to solve, please point me > to them and I'll take a look. You can take a look at saa7134-cards.c, for example. saa7134_tuner_setup() has several examples. It starts with this one: switch (dev->board) { case SAA7134_BOARD_BMK_MPEX_NOTUNER: case SAA7134_BOARD_BMK_MPEX_TUNER: /* Checks if the device has a tuner at 0x60 addr If the device doesn't have a tuner, TUNER_ABSENT will be used at tuner_type, avoiding loading tuner without needing it */ dev->i2c_client.addr = 0x60; board = (i2c_master_recv(&dev->i2c_client, &buf, 0) < 0) ? SAA7134_BOARD_BMK_MPEX_NOTUNER : SAA7134_BOARD_BMK_MPEX_TUNER; In this specific case, it is simply a probe for a device at address 0x60, but there are more complex cases there, with eeprom reads and/or some random init that happens before actually attaching some driver at the i2c address. It is known to work, but it sounds like a hack. Cheers, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html