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SubjectRe: [PATCH v3] iio: dac: mcp4902/mcp4912/mcp4922 dac driver
On 06/06/2014 03:12 AM, Michael Welling wrote:
[...]
> +enum mcp49x2_supported_device_ids {
> + ID_MCP4902,
> + ID_MCP4912,
> + ID_MCP4922,
> +};
> +
> +struct mcp49x2_state {
> + struct spi_device *spi;
> + unsigned int value[MCP49X2_NUM_CHANNELS];
> + unsigned int power_mode[MCP49X2_NUM_CHANNELS];
> + unsigned int vref_mv;
> + struct regulator *vref_reg;
> +};
> +
> +#define MCP49X2_CHAN(chan, bits) { \
> + .type = IIO_VOLTAGE, \
> + .output = 1, \
> + .indexed = 1, \
> + .channel = chan, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> + .scan_type = IIO_ST('u', bits, 16, 12-bits), \

The IIO_ST macro was removed a while ago, this will not compile with the
latest IIO sources.

> +}
> +
> +static int mcp49x2_spi_write(struct spi_device *spi, u8 addr, u32 val)
> +{
> + u8 mosi[2] ____cacheline_aligned;

It is also important that the transfer buffer is not on the stack and
strictly speaking the buffer should also be allocated with GFP_DMA.

> +
> + mosi[1] = val & 0xff;
> + mosi[0] = (addr == 0) ? 0x00 : 0x80;
> + mosi[0] |= 0x30 | ((val >> 8) & 0x0f);
> +
> + return spi_write(spi, mosi, 2);
> +}
[...]
> +
> +static int mcp49x2_probe(struct spi_device *spi)
> +{
> + struct iio_dev *indio_dev;
> + struct mcp49x2_state *state;
> + const struct spi_device_id *id;
> + int ret;
> +
> + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
> + if (indio_dev == NULL)
> + return -ENOMEM;
> +
> + state = iio_priv(indio_dev);
> + state->spi = spi;
> + state->vref_reg = devm_regulator_get(&spi->dev, "vref");
> + if (!IS_ERR(state->vref_reg)) {
> + ret = regulator_enable(state->vref_reg);
> + if (ret) {
> + dev_err(&spi->dev, "Failed to enable vref regulator: %d\n",
> + ret);
> + return ret;
> + }
> +
> + ret = regulator_get_voltage(state->vref_reg);
> + if (ret < 0) {
> + dev_err(&spi->dev, "Failed to read vref regulator: %d\n",
> + ret);
> + goto error_disable_reg;
> + }
> + state->vref_mv = ret / 1000;
> + } else {
> + dev_info(&spi->dev, "Vref regulator not specified assuming 2.5V\n");
> + state->vref_mv = 2500;

This is not a good idea, unless there is a built-in vref with 2.5V. If that
is the case use devm_regulator_get_optional() as devm_regulator_get() will
return a dummy regulator if no regulator was specified for the device.

> + }
> +
> + spi_set_drvdata(spi, indio_dev);
> + id = spi_get_device_id(spi);
> + indio_dev->dev.parent = &spi->dev;
> + indio_dev->info = &mcp49x2_info;
> + indio_dev->modes = INDIO_DIRECT_MODE;
> + indio_dev->channels = mcp49x2_channels[id->driver_data];
> + indio_dev->num_channels = MCP49X2_NUM_CHANNELS;
> + indio_dev->name = id->name;
> +
> + ret = devm_iio_device_register(&spi->dev, indio_dev);
> + if (ret) {
> + dev_err(&spi->dev, "Failed to register iio device: %d\n",
> + ret);
> + goto error_disable_reg;
> + }
> +
> + return 0;
> +
> +error_disable_reg:
> + if (!IS_ERR(state->vref_reg))
> + regulator_disable(state->vref_reg);
> +
> + return ret;
> +}




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