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Date: Sat, 5 Aug 2023 19:28:59 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Andrea Collamati <andrea.collamati@...il.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] iio: add MCP4728 I2C DAC driver
On Thu, 3 Aug 2023 14:56:35 +0200
Andrea Collamati <andrea.collamati@...il.com> wrote:
> MCP4728 is a 12-bit quad channel DAC with I2C interface.
>
> support for:
> * per-channel gain
> * per-channel power state
> * per-channel power down mode control
> * per-channel vref selection internal/vdd
> * store current state to on-chip EEPROM
>
> Signed-off-by: Andrea Collamati <andrea.collamati@...il.com>
Hi Andrea,
On this final read through I noticed a few minor things. Rather than
get you to do a v5 I've made the changes whilst applying. Please
take a sanity check at
https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/log/?h=testing
to make sure I didn't break anything and let me know if I did!
Applied with the below mentioned changes to the togreg branch of iio.git
which is initially pushed out as testing to let 0-day poke at it and see
if it can find any problems.
Thanks,
Jonathan
> diff --git a/drivers/iio/dac/mcp4728.c b/drivers/iio/dac/mcp4728.c
> new file mode 100644
> index 000000000000..ba3eab349b0a
> --- /dev/null
> +++ b/drivers/iio/dac/mcp4728.c
> @@ -0,0 +1,626 @@
...
> +
> +static int mcp4728_set_scale(int channel, struct mcp4728_data *data, int val,
> + int val2)
> +{
> + int scale = mcp4728_find_matching_scale(data, val, val2);
> +
> + if (scale < 0)
> + return scale;
> +
> + switch (scale) {
> + case MCP4728_SCALE_VDD:
> + data->chdata[channel].ref_mode = MCP4728_VREF_EXTERNAL_VDD;
> + break;
> + case MCP4728_SCALE_VINT_NO_GAIN:
> + data->chdata[channel].ref_mode = MCP4728_VREF_INTERNAL_2048mV;
> + data->chdata[channel].g_mode = MCP4728_GAIN_X1;
> + break;
> + case MCP4728_SCALE_VINT_GAIN_X2:
> + data->chdata[channel].ref_mode = MCP4728_VREF_INTERNAL_2048mV;
> + data->chdata[channel].g_mode = MCP4728_GAIN_X2;
> + break;
> + default:
> + return -EINVAL;
> + }
> + return 0;
return instead of breaking above as nothing to be done after the switch.
Side effect of that is this return 0 not needed.
> +}
...
> +static int mcp4728_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan, int val,
> + int val2, long mask)
> +{
> + struct mcp4728_data *data = iio_priv(indio_dev);
> + int ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + if (val < 0 || val > GENMASK(MCP4728_RESOLUTION - 1, 0))
> + return -EINVAL;
> + data->chdata[chan->channel].dac_value = val;
> + ret = mcp4728_program_channel_cfg(chan->channel, indio_dev);
> + break;
Direct returns preferred if no cleanup to do.
> + case IIO_CHAN_INFO_SCALE:
> + ret = mcp4728_set_scale(chan->channel, data, val, val2);
> + if (ret)
> + break;
> +
> + ret = mcp4728_program_channel_cfg(chan->channel, indio_dev);
> + break;
> + default:
> + ret = -EINVAL;
> + break;
> + }
> +
> + return ret;
> +}
> +static int mcp4728_init_channels_data(struct mcp4728_data *data)
> +{
> + u8 inbuf[MCP4728_READ_RESPONSE_LEN];
> + int ret;
> + unsigned int i;
> +
> + ret = i2c_master_recv(data->client, inbuf, MCP4728_READ_RESPONSE_LEN);
> + if (ret < 0) {
> + dev_err(&data->client->dev,
> + "failed to read mcp4728 conf. Err=%d\n", ret);
> + return ret;
As this is only called from probe, we should still use dev_err_probe() in here
as mentioned below.
> + } else if (ret != MCP4728_READ_RESPONSE_LEN) {
> + dev_err(&data->client->dev,
> + "failed to read mcp4728 conf. Wrong Response Len ret=%d\n",
> + ret);
> + return -EIO;
> + }
> +
> + for (i = 0; i < MCP4728_N_CHANNELS; i++) {
> + struct mcp4728_channel_data *ch = &data->chdata[i];
> + u8 r2 = inbuf[i * 6 + 1];
> + u8 r3 = inbuf[i * 6 + 2];
> +
> + ch->dac_value = FIELD_GET(MCP4728_DAC_H_MASK, r2) << 8 |
> + FIELD_GET(MCP4728_DAC_L_MASK, r3);
> + ch->ref_mode = FIELD_GET(MCP4728_VREF_MASK, r2);
> + ch->pd_mode = FIELD_GET(MCP4728_PDMODE_MASK, r2);
> + ch->g_mode = FIELD_GET(MCP4728_GAIN_MASK, r2);
> + }
> +
> + return 0;
> +}
...
> +static int mcp4728_probe(struct i2c_client *client)
> +{
> + const struct i2c_device_id *id = i2c_client_get_device_id(client);
> + struct mcp4728_data *data;
> + struct iio_dev *indio_dev;
> + int err;
> +
> + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + data = iio_priv(indio_dev);
> + i2c_set_clientdata(client, indio_dev);
> + data->client = client;
> +
> + data->vdd_reg = devm_regulator_get(&client->dev, "vdd");
> + if (IS_ERR(data->vdd_reg))
> + return PTR_ERR(data->vdd_reg);
> +
> + err = regulator_enable(data->vdd_reg);
> + if (err)
> + return err;
> +
> + err = devm_add_action_or_reset(&client->dev, mcp4728_reg_disable,
> + data->vdd_reg);
> + if (err)
> + return err;
> +
> + /* MCP4728 has internal EEPROM that save each channel boot configuration.
Trivial but comment syntax in IIO (there are some differences in a few other subsystems)
is
/*
* MCP...
> + * It means that device configuration is unknown to the driver at kernel boot.
> + * mcp4728_init_channels_data reads back DAC settings and stores them in data
> + * structure.
> + */
> + err = mcp4728_init_channels_data(data);
> + if (err) {
I'd missed this previously but dev_err_probe() has several advantages in that
it handles deferring neatly and also ends up with less code.
> + dev_err(&client->dev,
> + "failed to read mcp4728 current configuration\n");
> + return err;
> + }
> +
> + err = mcp4728_init_scales_avail(data);
> + if (err) {
> + dev_err(&client->dev, "failed to init scales\n");
> + return err;
> + }
> +
> + indio_dev->name = id->name;
> + indio_dev->info = &mcp4728_info;
> + indio_dev->channels = mcp4728_channels;
> + indio_dev->num_channels = MCP4728_N_CHANNELS;
> + indio_dev->modes = INDIO_DIRECT_MODE;
> +
> + return devm_iio_device_register(&client->dev, indio_dev);
> +}
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