linux-kernel - Re: [PATCHv1 2/2] Input: EXC3000: Add support to query model and fw

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Date:   Tue, 12 Nov 2019 16:23:39 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>
Cc:     Ahmet Inan <inan@...tec.de>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCHv1 2/2] Input: EXC3000: Add support to query model and
 fw_version

Hi Sebastian,

On Thu, Nov 07, 2019 at 07:10:10PM +0100, Sebastian Reichel wrote:
> Expose model and fw_version via sysfs. Also query the model
> in probe to make sure, that the I2C communication with the
> device works before successfully probing the driver.
> 
> Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
> ---
>  drivers/input/touchscreen/exc3000.c | 136 ++++++++++++++++++++++++++++
>  1 file changed, 136 insertions(+)
> 
> diff --git a/drivers/input/touchscreen/exc3000.c b/drivers/input/touchscreen/exc3000.c
> index 7d695022082c..4c9f132629b9 100644
> --- a/drivers/input/touchscreen/exc3000.c
> +++ b/drivers/input/touchscreen/exc3000.c
> @@ -41,6 +41,11 @@ struct exc3000_data {
>  	struct touchscreen_properties prop;
>  	struct timer_list timer;
>  	u8 buf[2 * EXC3000_LEN_FRAME];
> +	char model[11];
> +	char fw_version[6];
> +	struct completion wait_event;
> +	struct mutex query_lock;
> +	int query_result;
>  };
>  
>  static void exc3000_report_slots(struct input_dev *input,
> @@ -121,6 +126,35 @@ static int exc3000_read_data(struct i2c_client *client,
>  	return 0;
>  }
>  
> +static void exc3000_query_interrupt(struct exc3000_data *data)
> +{
> +	u8 *buf = data->buf;
> +	int err;
> +
> +	data->query_result = 0;
> +
> +	err = i2c_master_recv(data->client, buf, EXC3000_LEN_FRAME);
> +	if (err < 0) {
> +		data->query_result = err;
> +		goto out;
> +	}
> +
> +	if (buf[0] == 0x42 && buf[4] == 'E') {
> +		memcpy(data->model, buf+5, 10);
> +		data->model[10] = '\0';
> +		goto out;
> +	} else if (buf[0] == 0x42 && buf[4] == 'D') {
> +		memcpy(data->fw_version, buf+5, 5);
> +		data->fw_version[5] = '\0';
> +		goto out;
> +	}
> +
> +	data->query_result = -EPROTO;
> +
> +out:
> +	complete(&data->wait_event);
> +}
> +
>  static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
>  {
>  	struct exc3000_data *data = dev_id;
> @@ -129,6 +163,11 @@ static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
>  	int slots, total_slots;
>  	int error;
>  
> +	if (mutex_is_locked(&data->query_lock)) {
> +		exc3000_query_interrupt(data);
> +		goto out;
> +	}
> +
>  	error = exc3000_read_data(data->client, buf, &total_slots);
>  	if (error) {
>  		/* Schedule a timer to release "stuck" contacts */
> @@ -156,12 +195,92 @@ static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
>  	return IRQ_HANDLED;
>  }
>  
> +static int exc3000_get_fw_version(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct exc3000_data *data = dev_get_drvdata(dev);
> +	static const u8 request[68] =
> +		{0x67, 0x00, 0x42, 0x00, 0x03, 0x01, 'D', 0x00};
> +	struct i2c_client *client = data->client;
> +	int err;
> +
> +	mutex_lock(&data->query_lock);
> +
> +	data->query_result = -ETIMEDOUT;
> +	reinit_completion(&data->wait_event);
> +
> +	err = i2c_master_send(client, request, sizeof(request));
> +	if (err < 0) {
> +		mutex_unlock(&data->query_lock);
> +		return err;
> +	}
> +
> +	wait_for_completion_interruptible_timeout(&data->wait_event, 1*HZ);
> +	mutex_unlock(&data->query_lock);
> +
> +	if (data->query_result < 0)
> +		return data->query_result;
> +
> +	return sprintf(buf, "%s\n", data->fw_version);
> +}
> +static DEVICE_ATTR(fw_version, S_IRUGO, exc3000_get_fw_version, NULL);
> +
> +static ssize_t exc3000_get_model(struct exc3000_data *data)
> +{
> +	static const u8 request[68] =
> +		{0x67, 0x00, 0x42, 0x00, 0x03, 0x01, 'E', 0x00};
> +	struct i2c_client *client = data->client;
> +	int err;
> +
> +	mutex_lock(&data->query_lock);
> +	data->query_result = -ETIMEDOUT;
> +	reinit_completion(&data->wait_event);
> +
> +	err = i2c_master_send(client, request, sizeof(request));
> +	if (err < 0) {
> +		mutex_unlock(&data->query_lock);
> +		return err;
> +	}
> +
> +	wait_for_completion_interruptible_timeout(&data->wait_event, 1*HZ);
> +	mutex_unlock(&data->query_lock);
> +
> +	return data->query_result;
> +}
> +
> +static ssize_t exc3000_get_model_sysfs(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct exc3000_data *data = dev_get_drvdata(dev);
> +	int err = exc3000_get_model(data);

Do we really need to re-fetch model (and firmware ID) on each access?
Can we query it as probe time and cache? This I think would simplify the
driver, as you probably would not need to hook it into the ISR. Can you
just post a read/write transaction to fetch it without waiting for
interrupt? Or, if single transaction does not work and you need to wait
for certain time for response - just add msleep() and maybe mark driver
for async probe...

Thanks.

-- 
Dmitry