On Wed, 05 Jan 2011 20:02:41 -0200, Mauro Carvalho Chehab wrote:
> Em 05-01-2011 19:51, Jean Delvare escreveu:
> > 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
This call to i2c_master_recv() could be replaced easily with
i2c_transfer(), which doesn't require an i2c_client.
Alternatively, you could delay the probe until you are ready to
instantiate the tuner device, and use i2c_new_device() when you're sure
it's there, and i2c_new_probed_device() when you aren't. This would be
nicer, but this also requires non-trivial changes.
> 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.
For eeprom reads, I would definitely recommend getting a clean
i2c_client from i2c-core using i2c_new_dummy() or i2c_new_device().
For "random init", well, I guess each case is different, so I can't
make a general statement.
--
Jean Delvare
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