On Mon, Mar 19, 2018 at 05:47:05PM +0100, Peter Rosin wrote:
> On 2018-03-19 17:10, Guenter Roeck wrote:
> > Commit dde67eb1beeb ("i2c: add i2c_get_device_id() to get the standard
> > I2C device id") added a function to return the standard I2C device ID.
> > Use that function to verify the device ID of a given device.
>
> Yeah, you're moving complexity from the driver to the core, reducing
> the indentation level and generally make things look neater. In fact,
> I thought about adding something like this, but didn't since I only had
> the one user.
>
> The only negative is the added line count, but I suppose more drivers
> will call this function down the line so it should be a net win in the
> long run. There was the PCA9641 chip earlier today e.g., but maybe we
> should wait for more device id users?
>
Unfortunately it looks like only NXPs GPIO expanders and i2c muxes support
it, or at least I didn't find any other chips. I figured though that it
would be worth it even if only two drivers (or even one) end up using it.
> I wonder when other manufacturers will get on board?
>
Hah, good question. As mentioned above, I didn't find any.
> I also wonder if NXP will ever release a chip with part-id 0 and
> die-revision 0? If not, an all zero struct i2c_device_identity
> could be used instead of manufacturer_id 0xffff and that would
> simplify the pca954x driver code a bit more. But I guess we can
> never know the answer to that question. And even if we did, the
> answer might change later. But it would be nice...
>
That would be nice. You could ask at i2c.support@xxxxxxx, but I guess
it would always be somewhat risky since the standard doesn't restrict
its use, and some product manager at NXP might decide in the future
that a device ID of 0x00 would be "cool".
Guenter
> > Cc: Peter Rosin <peda@xxxxxxxxxx>
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> > RFC:
> > - Compile tested only
>
> Can't test either since I have no chips, but the code looks good.
>
> Adrian have HW, but maybe he's getting tried of testing?
>
> Hmmm, for testing purposes it would be nice if a linux slave device
> implemented this. But I don't have HW that supports that either so it
> wouldn't help *me* anyway...
>
> Anyway, ack from me for both patches. But maybe I'm the one
> picking them up? Wolfram?
>
> Cheers,
> Peter
>
> > - Should there also be I2C_DEVICE_PART_ID_ANY to enable maching
> > against all parts from a given manufacturer ?
> >
> > drivers/i2c/i2c-core-base.c | 34 ++++++++++++++++++++++++++++++++++
> > include/linux/i2c.h | 3 +++
> > 2 files changed, 37 insertions(+)
> >
> > diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> > index 16a3b73375a6..4e4372b064f6 100644
> > --- a/drivers/i2c/i2c-core-base.c
> > +++ b/drivers/i2c/i2c-core-base.c
> > @@ -2009,6 +2009,40 @@ int i2c_get_device_id(const struct i2c_client *client,
> > }
> > EXPORT_SYMBOL_GPL(i2c_get_device_id);
> >
> > +/**
> > + * i2c_verify_device_id - verify device ID
> > + * @client: The device to query
> > + * @id: Expected device ID
> > + *
> > + * Returns negative errno on error, zero on success.
> > + */
> > +int i2c_verify_device_id(const struct i2c_client *client,
> > + const struct i2c_device_identity *id)
> > +{
> > + struct i2c_device_identity real_id;
> > + int ret;
> > +
> > + if (id->manufacturer_id == I2C_DEVICE_ID_NONE)
> > + return 0;
> > +
> > + ret = i2c_get_device_id(client, &real_id);
> > + if (ret < 0)
> > + return ret;
> > +
> > + if (id->manufacturer_id != real_id.manufacturer_id ||
> > + id->part_id != real_id.part_id ||
> > + (id->die_revision != I2C_DEVICE_DIE_REVISION_ANY &&
> > + id->die_revision != real_id.die_revision)) {
> > + dev_err(&client->dev, "unexpected device id %03x-%03x-%x\n",
> > + real_id.manufacturer_id, real_id.part_id,
> > + real_id.die_revision);
> > + return -ENODEV;
> > + }
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(i2c_verify_device_id);
> > +
> > /* ----------------------------------------------------
> > * the i2c address scanning function
> > * Will not work for 10-bit addresses!
> > diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> > index 44ad14e016b5..45bae9717ecb 100644
> > --- a/include/linux/i2c.h
> > +++ b/include/linux/i2c.h
> > @@ -189,6 +189,8 @@ i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
> > u8 command, u8 length, u8 *values);
> > int i2c_get_device_id(const struct i2c_client *client,
> > struct i2c_device_identity *id);
> > +int i2c_verify_device_id(const struct i2c_client *client,
> > + const struct i2c_device_identity *id);
> > #endif /* I2C */
> >
> > /**
> > @@ -216,6 +218,7 @@ struct i2c_device_identity {
> > #define I2C_DEVICE_ID_NONE 0xffff
> > u16 part_id;
> > u8 die_revision;
> > +#define I2C_DEVICE_DIE_REVISION_ANY 0xff
> > };
> >
> > enum i2c_alert_protocol {
> >
>
