Re: [PATCH v4 2/3] iio: adc: Support ROHM BD79112 ADC/GPIO

Matti Vaittinen
2025-09-12T09:30:51Z

On 12/09/2025 00:20, David Lechner wrote:
> On 9/10/25 6:24 AM, Matti Vaittinen wrote:
>
> ...
>
>> diff --git a/drivers/iio/adc/rohm-bd79112.c b/drivers/iio/adc/rohm-bd79112.c
>> new file mode 100644
>> index 0000000000000000000000000000000000000000..a2a3affe2c6dc86a237a164139c27ec66dc9d131
>> --- /dev/null
>> +++ b/drivers/iio/adc/rohm-bd79112.c
>> @@ -0,0 +1,553 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * ROHM ADC driver for BD79112 signal monitoring hub.
>> + * Copyright (C) 2025, ROHM Semiconductor.
>> + *
>> + * SPI communication derived from ad7923.c and ti-ads7950.c
>
> Really? I wrote the ti-ads7950 driver and I can't say I see the
> resemblance. ;-)

Really. :) I picked the idea of populating the transfers in the probe
and using buffers from the driver-data, from these drivers :) Well, I
admit it ended up being a bit different - but the starting point was
those drivers ;)

>
>> + */
>> +
>
> ...
>
>> +static int bd79112_get_gpio_pins(const struct iio_chan_spec *cs, int num_channels)
>
> u32 would make more sense when dealing with bit flags.
>
>> +{
>> + int i, gpio_channels;
>
> same for the local variable.

Meh. Ok :)

> ...
>
>> +static int bd79112_probe(struct spi_device *spi)
>> +{
>
> ...
>
>> +
>> + data->read_xfer[0].tx_buf = &data->read_tx[0];
>> + data->read_xfer[0].len = sizeof(data->read_tx);
>> + data->read_xfer[0].cs_change = 1;
>> + data->read_xfer[1].rx_buf = &data->read_rx;
>> + data->read_xfer[1].len = sizeof(data->read_rx);
>> + spi_message_init_with_transfers(&data->read_msg, data->read_xfer, 2);
>> +
>> + data->write_xfer.tx_buf = &data->reg_write_tx[0];
>> + data->write_xfer.len = sizeof(data->reg_write_tx);
>> + spi_message_init_with_transfers(&data->write_msg, &data->write_xfer, 1);
>
> If these messages never change (other than the data in the buffers), you can
> call devm_spi_optimize_message() here on each message to get reduced CPU usage
> on every SPI message for free.
>

Thanks!

Yours,
-- Matti