Re: [PATCH 3/5] hwmon: (pmbus/core) Add mapping function to pmbus_read_block_data()

On Thu, Jul 30, 2026 at 07:47:37AM -0700, Guenter Roeck wrote:
> On 7/30/26 07:27, Nuno Sá wrote:
> > On Tue, Jul 28, 2026 at 02:05:53PM -0700, Guenter Roeck wrote:
> > > On 7/28/26 09:03, Nuno Sá via B4 Relay wrote:
> > > > From: Nuno Sá <[email protected]>
> > > > 
> > > > This is in preparation for adding support to a device which needs to
> > > > use it's own read_block implementation.
> > > > 
> > > 
> > > The chip-specific implementation calls i2c_smbus_read_i2c_block_data().
> > > I'll need to know if this is a chip limit or a controller limit.
> > > If it is a controller limit, a chip specific override would be
> > > inappropriate.
> > 
> > I'll reply from top of my head (did not looked at the driver again).
> > IIRC, the biggest reason we need the chip-specific implementation is because of
> > the RAIL selection logic (mainly when not in page mode).
> > 
> 
> Yes, I have seen that. Question is why you use i2c_smbus_read_i2c_block_data()
> instead of i2c_smbus_read_block_data(). The rail selection logic would not
> require that.

IIRC the reason was because the i2c controller on the raspberry pie does not
support i2c_smbus_read_block_data(). So I guess this:

https://elixir.bootlin.com/linux/v7.1.4/source/drivers/i2c/i2c-core-smbus.c#L220

- Nuno Sá

> 
> Thanks,
> Guenter
>