[v2] Input: driver for the Goodix touchpanel

Hi Bastien,

On Wed, Sep 24, 2014 at 04:43:58PM +0200, Bastien Nocera wrote:
> Add a driver for the Goodix touchscreen panel found in Onda v975w
> tablets. The driver is based off the Android driver gt9xx.c found
> in some Android code dumps, but now bears no resemblance to the original
> driver.
> 
> The driver was tested on the aforementioned tablet.

I was looking over the driver once again and I have a few concerns.

> 
> Signed-off-by: Bastien Nocera <hadess@hadess.net>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> Tested-by: Bastien Nocera <hadess@hadess.net>
> ---
>  MAINTAINERS                        |   6 +
>  drivers/input/touchscreen/Kconfig  |  13 ++
>  drivers/input/touchscreen/Makefile |   1 +
>  drivers/input/touchscreen/goodix.c | 423 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 443 insertions(+)
>  create mode 100644 drivers/input/touchscreen/goodix.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 670b3dc..7a37464 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -4057,6 +4057,12 @@ L:	linux-media@vger.kernel.org
>  S:	Maintained
>  F:	drivers/media/usb/go7007/
>  
> +GOODIX TOUCHSCREEN
> +M:	Bastien Nocera <hadess@hadess.net>
> +L:	linux-input@vger.kernel.org
> +S:	Maintained
> +F:	drivers/input/touchscreen/goodix.c
> +
>  GPIO SUBSYSTEM
>  M:	Linus Walleij <linus.walleij@linaro.org>
>  M:	Alexandre Courbot <gnurou@gmail.com>
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index 6bb9a7d..c328df3 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -283,6 +283,19 @@ config TOUCHSCREEN_FUJITSU
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called fujitsu-ts.
>  
> +config TOUCHSCREEN_GOODIX
> +	tristate "Goodix I2C touchscreen"
> +	depends on I2C && ACPI
> +	help
> +	  Say Y here if you have the Goodix touchscreen (such as one
> +	  installed in Onda v975w tablets) connected to your
> +	  system.
> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called goodix.
> +
>  config TOUCHSCREEN_ILI210X
>  	tristate "Ilitek ILI210X based touchscreen"
>  	depends on I2C
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index 4be94fc..55af212 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -33,6 +33,7 @@ obj-$(CONFIG_TOUCHSCREEN_EETI)		+= eeti_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_ELO)		+= elo.o
>  obj-$(CONFIG_TOUCHSCREEN_EGALAX)	+= egalax_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_FUJITSU)	+= fujitsu_ts.o
> +obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix.o
>  obj-$(CONFIG_TOUCHSCREEN_ILI210X)	+= ili210x.o
>  obj-$(CONFIG_TOUCHSCREEN_INEXIO)	+= inexio.o
>  obj-$(CONFIG_TOUCHSCREEN_INTEL_MID)	+= intel-mid-touch.o
> diff --git a/drivers/input/touchscreen/goodix.c b/drivers/input/touchscreen/goodix.c
> new file mode 100644
> index 0000000..fd02b5e
> --- /dev/null
> +++ b/drivers/input/touchscreen/goodix.c
> @@ -0,0 +1,423 @@
> +/*
> + *  driver for Goodix Touchscreens
> + *
> + *  Copyright (c) 2014 Red Hat Inc.
> + *
> + *  This code is based on gt9xx.c authored by andrew@goodix.com:
> + *
> + *  2010 - 2012 Goodix Technology.
> + */
> +
> +/*
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License as published by the Free
> + * Software Foundation; version 2 of the License.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/i2c.h>
> +#include <linux/input.h>
> +#include <linux/input/mt.h>
> +#include <linux/module.h>
> +#include <linux/delay.h>
> +#include <linux/irq.h>
> +#include <linux/interrupt.h>
> +#include <linux/slab.h>
> +#include <asm/unaligned.h>
> +
> +struct goodix_ts_data {
> +	struct i2c_client *client;
> +	struct input_dev *input_dev;
> +	int abs_x_max;
> +	int abs_y_max;
> +	unsigned int max_touch_num;
> +	unsigned int int_trigger_type;
> +};
> +
> +#define GOODIX_MAX_HEIGHT		4096
> +#define GOODIX_MAX_WIDTH		4096
> +#define GOODIX_INT_TRIGGER		1
> +#define GOODIX_MAX_TOUCH		10
> +
> +#define GOODIX_CONFIG_MAX_LENGTH	240
> +
> +/* Register defineS */
> +#define GOODIX_READ_COOR_ADDR		0x814E
> +#define GOODIX_REG_CONFIG_DATA		0x8047
> +#define GOODIX_REG_VERSION		0x8140
> +
> +#define RESOLUTION_LOC		1
> +#define TRIGGER_LOC		6
> +
> +static const char *goodix_ts_name = "Goodix Capacitive TouchScreen";
> +static const unsigned long goodix_irq_flags[] = {
> +	IRQ_TYPE_EDGE_RISING,
> +	IRQ_TYPE_EDGE_FALLING,
> +	IRQ_TYPE_LEVEL_LOW,
> +	IRQ_TYPE_LEVEL_HIGH,
> +};
> +
> +/**
> + * goodix_i2c_read - read data from a register of the i2c slave device.
> + *
> + * @client: i2c device.
> + * @reg: the register to read from.
> + * @buf: raw write data buffer.
> + * @len: length of the buffer to write
> + */
> +static int goodix_i2c_read(struct i2c_client *client,
> +				u16 reg, u8 *buf, int len)
> +{
> +	struct i2c_msg msgs[2];
> +	u16 wbuf = cpu_to_be16(reg);
> +	int ret;
> +
> +	msgs[0].flags = 0;
> +	msgs[0].addr  = client->addr;
> +	msgs[0].len   = 2;
> +	msgs[0].buf   = (u8 *) &wbuf;
> +
> +	msgs[1].flags = I2C_M_RD;
> +	msgs[1].addr  = client->addr;
> +	msgs[1].len   = len;
> +	msgs[1].buf   = buf;
> +
> +	ret = i2c_transfer(client->adapter, msgs, 2);
> +	return ret < 0 ? ret : (ret != ARRAY_SIZE(msgs) ? -EIO : 0);
> +}
> +
> +/**
> + * goodix_i2c_write - write data to the i2c slave device.
> + *
> + * @client: i2c device.
> + * @reg: the register to read to.
> + * @buf: raw write data buffer.
> + * @len: length of the buffer to write
> + */
> +static int goodix_i2c_write(struct i2c_client *client,
> +				u16 reg, u8 *buf, int len)
> +{
> +	struct i2c_msg msg;
> +	int ret;
> +	u8 *wbuf;
> +	u16 *addr;
> +
> +	wbuf = kzalloc(len + 2, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	addr = ((u16 *) &wbuf[0]);
> +	*addr = cpu_to_be16(reg);
> +	memcpy(&wbuf[2], buf, len);
> +
> +	msg.flags = 0;
> +	msg.addr  = client->addr;
> +	msg.len   = len + 2;
> +	msg.buf   = wbuf;
> +
> +	ret = i2c_transfer(client->adapter, &msg, 1);
> +	kfree(wbuf);
> +	return ret < 0 ? ret : (ret != 1 ? -EIO : 0);
> +}
> +
> +static int goodix_ts_read_input_report(struct goodix_ts_data *ts, u8 *data)
> +{
> +	int touch_num;
> +	int ret;
> +
> +	ret = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR, data, 10);
> +	if (ret < 0) {
> +		dev_err(&ts->client->dev, "I2C transfer error (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	touch_num = data[0] & 0x0f;
> +	if (touch_num > GOODIX_MAX_TOUCH)
> +		return -EPROTO;
> +
> +	if (touch_num > 1) {
> +		ret = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR + 10,
> +				   &data[10], 8 * (touch_num - 1));
> +		if (ret < 0)
> +			return ret;
> +	}

I am a bit confused about this function. It looks like contact packet
size is 8 bytes, and they preceded by a byte with total number of
contacts reported, so why instead of 9 bytes we are reading 10?

> +
> +	return touch_num;
> +}
> +
> +static void goodix_ts_parse_touch(struct goodix_ts_data *ts, u8 *coor_data)
> +{
> +	int id = coor_data[0] & 0x0F;
> +	int input_x = get_unaligned_le16(&coor_data[1]);
> +	int input_y = get_unaligned_le16(&coor_data[3]);
> +	int input_w = get_unaligned_le16(&coor_data[5]);
> +
> +	input_mt_slot(ts->input_dev, id);
> +	input_mt_report_slot_state(ts->input_dev, MT_TOOL_FINGER, true);
> +	input_report_abs(ts->input_dev, ABS_MT_POSITION_X, input_x);
> +	input_report_abs(ts->input_dev, ABS_MT_POSITION_Y, input_y);
> +	input_report_abs(ts->input_dev, ABS_MT_TOUCH_MAJOR, input_w);
> +	input_report_abs(ts->input_dev, ABS_MT_WIDTH_MAJOR, input_w);
> +}
> +
> +/**
> + * goodix_process_events - Process incoming events
> + *
> + * @ts: our goodix_ts_data pointer
> + *
> + * Called when the IRQ is triggered. Read the current device state, and push
> + * the input events to the user space.
> + */
> +static void goodix_process_events(struct goodix_ts_data *ts)
> +{
> +	u8  point_data[1 + 8 * GOODIX_MAX_TOUCH + 1];

Here again, why do we need extra byte?

> +	int touch_num;
> +	int i;
> +
> +	touch_num = goodix_ts_read_input_report(ts, point_data);
> +	if (touch_num < 0)
> +		return;
> +
> +	for (i = 0; i < touch_num; i++)
> +		goodix_ts_parse_touch(ts, &point_data[1 + 8 * i]);
> +
> +	input_mt_sync_frame(ts->input_dev);
> +	input_sync(ts->input_dev);
> +}
> +
> +/**
> + * goodix_ts_irq_handler - The IRQ handler
> + *
> + * @irq: interrupt number.
> + * @dev_id: private data pointer.
> + */
> +static irqreturn_t goodix_ts_irq_handler(int irq, void *dev_id)
> +{
> +	struct goodix_ts_data *ts = dev_id;
> +	u8  end_cmd[1] = {0};
> +
> +	goodix_process_events(ts);
> +
> +	if (goodix_i2c_write(ts->client,
> +				GOODIX_READ_COOR_ADDR, end_cmd, 1) < 0)
> +		dev_err(&ts->client->dev, "I2C write end_cmd error");

I am not happy that we need to allocate/deallocate memory for each
interrupt. We only write one command to the driver, we could simply use
i2c_master_send() with a constant buffer.

BTW, you need terminate kernel messages with \n.

Also, below is a patch with a few assorted changes that I'd like you to
try if you have time.

Thanks!

[v2] Input: driver for the Goodix touchpanel

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