Re: [RFC 7/7] [media] rc: add support for IR LEDs driven through SPI

[Sean Young <sean@mess.org>]

On Wed, Jul 20, 2016 at 12:56:58AM +0900, Andi Shyti wrote:
> The ir-spi is a simple device driver which supports the
> connection between an IR LED and the MOSI line of an SPI device.
> 
> The driver, indeed, uses the SPI framework to stream the raw data
> provided by userspace through a character device. The chardev is
> handled by the LIRC framework and its functionality basically
> provides:
> 
>  - raw write: data to be sent to the SPI and then streamed to the
>    MOSI line;
>  - set frequency: sets the frequency whith which the data should
>    be sent;
> 
> The character device is created under /dev/lircX name, where X is
> and ID assigned by the LIRC framework.
> 
> Example of usage:
> 
>         fd = open("/dev/lirc0", O_RDWR);
>         if (fd < 0)
>                 return -1;
> 
>         val = 608000;
>         ret = ioctl(fd, LIRC_SET_SEND_CARRIER, &val);
>         if (ret < 0)
>                 return -1;
> 
>         n = write(fd, buffer, BUF_LEN);
>         if (n < 0 || n != BUF_LEN)
>                 ret = -1;
> 
>         close(fd);
> 
> Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
> ---
>  drivers/media/rc/Kconfig  |   9 ++++
>  drivers/media/rc/Makefile |   1 +
>  drivers/media/rc/ir-spi.c | 133 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 143 insertions(+)
>  create mode 100644 drivers/media/rc/ir-spi.c
> 
> diff --git a/drivers/media/rc/Kconfig b/drivers/media/rc/Kconfig
> index bd4d685..dacaa29 100644
> --- a/drivers/media/rc/Kconfig
> +++ b/drivers/media/rc/Kconfig
> @@ -261,6 +261,15 @@ config IR_REDRAT3
>  	   To compile this driver as a module, choose M here: the
>  	   module will be called redrat3.
>  
> +config IR_SPI
> +	tristate "SPI connected IR LED"
> +	depends on SPI && LIRC
> +	---help---
> +	  Say Y if you want to use an IR LED connected through SPI bus.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called ir-spi.
> +
>  config IR_STREAMZAP
>  	tristate "Streamzap PC Remote IR Receiver"
>  	depends on USB_ARCH_HAS_HCD
> diff --git a/drivers/media/rc/Makefile b/drivers/media/rc/Makefile
> index 379a5c0..1417c8d 100644
> --- a/drivers/media/rc/Makefile
> +++ b/drivers/media/rc/Makefile
> @@ -27,6 +27,7 @@ obj-$(CONFIG_IR_NUVOTON) += nuvoton-cir.o
>  obj-$(CONFIG_IR_ENE) += ene_ir.o
>  obj-$(CONFIG_IR_REDRAT3) += redrat3.o
>  obj-$(CONFIG_IR_RX51) += ir-rx51.o
> +obj-$(CONFIG_IR_SPI) += ir-spi.o
>  obj-$(CONFIG_IR_STREAMZAP) += streamzap.o
>  obj-$(CONFIG_IR_WINBOND_CIR) += winbond-cir.o
>  obj-$(CONFIG_RC_LOOPBACK) += rc-loopback.o
> diff --git a/drivers/media/rc/ir-spi.c b/drivers/media/rc/ir-spi.c
> new file mode 100644
> index 0000000..7b6f344
> --- /dev/null
> +++ b/drivers/media/rc/ir-spi.c
> @@ -0,0 +1,133 @@
> +/*
> + * Copyright (c) 2016 Samsung Electronics Co., Ltd.
> + * Author: Andi Shyti <andi.shyti@samsung.it>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * SPI driven IR LED device driver
> + */
> +
> +#include <linux/fs.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of_gpio.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +#include <media/rc-core.h>
> +
> +#define IR_SPI_DRIVER_NAME		"ir-spi"
> +
> +#define IR_SPI_DEFAULT_FREQUENCY	38000
> +#define IR_SPI_BIT_PER_WORD		    8
> +
> +struct ir_spi_data {
> +	struct rc_dev *rc;
> +	struct spi_device *spi;
> +	struct spi_transfer xfer;
> +	struct mutex mutex;
> +	struct regulator *regulator;
> +};
> +
> +static int ir_spi_tx(struct rc_dev *dev, unsigned *buffer, unsigned n)
> +{
> +	int ret;
> +	struct ir_spi_data *idata = (struct ir_spi_data *) dev->priv;

No cast needed.

> +
> +	ret = regulator_enable(idata->regulator);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&idata->mutex);
> +	idata->xfer.len = n;
> +	idata->xfer.tx_buf = buffer;
> +	mutex_unlock(&idata->mutex);

I'm not convinced the locking works here. You want to guard against 
someone modifying xfer while you are sending (so in spi_sync_transfer), 
which this locking is not doing. You could declare a 
local "struct spi_transfer xfer" and avoid the mutex altogether.

As discussed here you should be converting from pulse-space also.

> +
> +	ret = spi_sync_transfer(idata->spi, &idata->xfer, 1);
> +	if (ret)
> +		dev_err(&idata->spi->dev, "unable to deliver the signal\n");
> +
> +	regulator_disable(idata->regulator);
> +
> +	return ret;
> +}
> +
> +static int ir_spi_set_tx_carrier(struct rc_dev *dev, u32 carrier)
> +{
> +	struct ir_spi_data *idata = (struct ir_spi_data *) dev->priv;

No cast needed here.

> +
> +	if (!carrier)
> +		return -EINVAL;
> +
> +	mutex_lock(&idata->mutex);
> +	idata->xfer.speed_hz = carrier;
> +	mutex_unlock(&idata->mutex);
> +
> +	return 0;
> +}
> +
> +static int ir_spi_probe(struct spi_device *spi)
> +{
> +	int ret;
> +	struct ir_spi_data *idata;
> +
> +	idata = devm_kzalloc(&spi->dev, sizeof(*idata), GFP_KERNEL);
> +	if (!idata)
> +		return -ENOMEM;
> +
> +	idata->regulator = devm_regulator_get(&spi->dev, "irda_regulator");
> +	if (IS_ERR(idata->regulator))
> +		return PTR_ERR(idata->regulator);
> +
> +	idata->rc = rc_allocate_device(RC_DRIVER_IR_RAW_TX);
> +	if (!idata->rc)
> +		return -ENOMEM;
> +
> +	idata->rc->s_tx_carrier = ir_spi_set_tx_carrier;
> +	idata->rc->tx_ir = ir_spi_tx;
> +	idata->rc->driver_name = IR_SPI_DRIVER_NAME;
> +	idata->rc->priv = idata;
> +
> +        ret = rc_register_device(idata->rc);
> +	if (ret)
> +		return ret;

You could really call rc_register_device() once the rc_dev device is 
ready, so after the mutex_init() etc. In practise I don't think it 
matters, since udev has to create the device and then someone has to 
do a open and either write or ioctl(LIRC_SET_SEND_CARRIER). Surely the 
following code has executed by then.

> +
> +	mutex_init(&idata->mutex);
> +
> +	idata->spi = spi;
> +
> +	idata->xfer.bits_per_word = IR_SPI_BIT_PER_WORD;
> +	idata->xfer.speed_hz = IR_SPI_DEFAULT_FREQUENCY;
> +
> +	return 0;
> +}
> +
> +static int ir_spi_remove(struct spi_device *spi)
> +{
> +	struct ir_spi_data *idata = spi_get_drvdata(spi);
> +
> +	rc_unregister_device(idata->rc);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id ir_spi_of_match[] = {
> +	{ .compatible = "ir-spi" },
> +	{},
> +};
> +
> +static struct spi_driver ir_spi_driver = {
> +	.probe = ir_spi_probe,
> +	.remove = ir_spi_remove,
> +	.driver = {
> +		.name = IR_SPI_DRIVER_NAME,
> +		.of_match_table = ir_spi_of_match,
> +	},
> +};
> +
> +module_spi_driver(ir_spi_driver);
> +
> +MODULE_AUTHOR("Andi Shyti <andi.shyti@samsung.com>");
> +MODULE_DESCRIPTION("SPI IR LED");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.8.1
> 
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