[PATCH 3/3] backlight: tdo24m: add model and status sysfs entries

[Robert Jarzmik <robert.jarzmik@free.fr>]

Add entries to query the panel ASIC to acquire the model number and the
status field. This comes in handy to check that the SPI connection is
functional and that the panel's firmware is alive.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
---
 drivers/video/backlight/tdo24m.c | 73 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/tdo24m.c b/drivers/video/backlight/tdo24m.c
index e4b2dfabf192..113c28c2145a 100644
--- a/drivers/video/backlight/tdo24m.c
+++ b/drivers/video/backlight/tdo24m.c
@@ -22,7 +22,7 @@
 
 #define POWER_IS_ON(pwr)	((pwr) <= FB_BLANK_NORMAL)
 
-#define TDO24M_SPI_BUFF_SIZE	(4)
+#define TDO24M_SPI_BUFF_SIZE	(6)
 #define MODE_QVGA	0
 #define MODE_VGA	1
 
@@ -33,6 +33,7 @@ struct tdo24m {
 	struct spi_message	msg;
 	struct spi_transfer	xfer;
 	uint8_t			*buf;
+	uint8_t			*rx_buf;
 	struct gpio_desc	*xres;
 
 	int (*adj_mode)(struct tdo24m *lcd, int mode);
@@ -219,6 +220,30 @@ static int tdo24m_writes(struct tdo24m *lcd, const uint32_t *array)
 	return err;
 }
 
+static int tdo24m_read_command(struct tdo24m *lcd, unsigned char cmd,
+			       unsigned int *id)
+{
+	struct spi_transfer *x = &lcd->xfer;
+	int err = 0, i;
+
+	lcd->buf[0] = cmd >> 1;
+	lcd->buf[1] = (cmd & 0x01) << 7;
+	lcd->buf[2] = 0;
+	lcd->buf[3] = 0;
+	lcd->buf[4] = 0;
+
+	x->len = 6;
+	err = spi_sync(lcd->spi_dev, &lcd->msg);
+
+	for (i = 0; i < sizeof(lcd->rx_buf) - 2; i++)
+		lcd->rx_buf[i] = (lcd->rx_buf[i + 1] << 2) |
+			(lcd->rx_buf[i + 2] >> 6);
+	*id = (lcd->rx_buf[0] << 24) | (lcd->rx_buf[1] << 16) |
+		(lcd->rx_buf[2] << 8) | lcd->rx_buf[3];
+
+	return err;
+}
+
 static int tdo24m_adj_mode(struct tdo24m *lcd, int mode)
 {
 	switch (mode) {
@@ -327,6 +352,43 @@ static int tdo24m_set_mode(struct lcd_device *ld, struct fb_videomode *m)
 	return lcd->adj_mode(lcd, mode);
 }
 
+static ssize_t tdo24m_model_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct tdo24m *lcd = dev_get_drvdata(dev);
+	uint32_t data;
+	int err;
+
+	err = tdo24m_read_command(lcd, 0x04, &data);
+	if (!err)
+		return snprintf(buf, PAGE_SIZE, "0x%06x\n", data >> 8);
+
+	return err;
+}
+static DEVICE_ATTR_RO(tdo24m_model);
+
+static ssize_t tdo24m_status_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct tdo24m *lcd = dev_get_drvdata(dev);
+	uint32_t data;
+	int err;
+
+	err = tdo24m_read_command(lcd, 0x09, &data);
+	if (!err)
+		return snprintf(buf, PAGE_SIZE, "0x%08x\n", data);
+
+	return err;
+}
+static DEVICE_ATTR_RO(tdo24m_status);
+
+static struct attribute *tdo24m_attrs[] = {
+	&dev_attr_tdo24m_model.attr,
+	&dev_attr_tdo24m_status.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(tdo24m);
+
 static struct lcd_ops tdo24m_ops = {
 	.get_power	= tdo24m_get_power,
 	.set_power	= tdo24m_set_power,
@@ -365,6 +427,9 @@ static int tdo24m_probe(struct spi_device *spi)
 	lcd->buf = devm_kzalloc(&spi->dev, TDO24M_SPI_BUFF_SIZE, GFP_KERNEL);
 	if (lcd->buf = NULL)
 		return -ENOMEM;
+	lcd->rx_buf = devm_kzalloc(&spi->dev, TDO24M_SPI_BUFF_SIZE, GFP_KERNEL);
+	if (lcd->rx_buf = NULL)
+		return -ENOMEM;
 
 	lcd->xres = devm_gpiod_get(&spi->dev, "reset", GPIOD_OUT_LOW);
 	m = &lcd->msg;
@@ -374,6 +439,7 @@ static int tdo24m_probe(struct spi_device *spi)
 
 	x->cs_change = 0;
 	x->tx_buf = &lcd->buf[0];
+	x->rx_buf = &lcd->rx_buf[0];
 	spi_message_add_tail(x, m);
 
 	switch (model) {
@@ -396,6 +462,11 @@ static int tdo24m_probe(struct spi_device *spi)
 		return PTR_ERR(lcd->lcd_dev);
 
 	spi_set_drvdata(spi, lcd);
+
+	err = devm_device_add_groups(&spi->dev, tdo24m_groups);
+	if (err)
+		return err;
+
 	err = tdo24m_power(lcd, FB_BLANK_UNBLANK);
 	if (err)
 		return err;
-- 
2.11.0