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Date: Mon, 17 Dec 2012 11:50:48 -0500
From: "devendra.aaru" <devendra.aaru@...il.com>
To: Jingoo Han <jg1.han@...sung.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Richard Purdie <rpurdie@...ys.net>
Subject: Re: PATCH] backlight: add lms501kf03 LCD driver
Hello,
> +static int lms501kf03_spi_write(struct lms501kf03 *lcd, unsigned char address,
> + unsigned char command)
> +{
> + int ret;
> +
> + ret = lms501kf03_spi_write_byte(lcd, address, command);
> +
> + return ret;
there is redundancy here,
you can do just removing the ret and do return.
> +}
> +
> +static int lms501kf03_panel_send_sequence(struct lms501kf03 *lcd,
> + const unsigned short *wbuf)
> +{
> + int ret = 0, i = 0;
> +
> + while (wbuf[i] != ENDDEF) {
> + if (i == 0)
> + ret = lms501kf03_spi_write(lcd, COMMAND_ONLY, wbuf[i]);
> + else
> + ret = lms501kf03_spi_write(lcd, DATA_ONLY, wbuf[i]);
> + if (ret)
> + break;
> + i += 1;
> + }
> +
> + return ret;
> +}
> +
> +static int lms501kf03_ldi_init(struct lms501kf03 *lcd)
> +{
> + int ret, i;
> + static const unsigned short *init_seq[] = {
> + seq_password,
> + seq_power,
> + seq_display,
> + seq_rgb_if,
> + seq_display_inv,
> + seq_vcom,
> + seq_gate,
> + seq_panel,
> + seq_col_mod,
> + seq_w_gamma,
> + seq_rgb_gamma,
> + seq_sleep_out,
> + };
> +
> + for (i = 0; i < ARRAY_SIZE(init_seq); i++) {
> + ret = lms501kf03_panel_send_sequence(lcd, init_seq[i]);
> + if (ret)
> + break;
> + }
> + /* according to the datasheet, 120ms delay time is required. */
why the 120ms delay required would be good to specify as comment. or
you can put the link to datasheet if available.
> + msleep(120);
> +
> + return ret;
> +}
> +
> +static int lms501kf03_ldi_enable(struct lms501kf03 *lcd)
> +{
> + return lms501kf03_panel_send_sequence(lcd, seq_display_on);
> +}
> +
> +static int lms501kf03_ldi_disable(struct lms501kf03 *lcd)
> +{
> + return lms501kf03_panel_send_sequence(lcd, seq_display_off);
> +}
> +
> +static int lms501kf03_power_is_on(int power)
> +{
> + return (power) <= FB_BLANK_NORMAL;
> +}
> +
> +static int lms501kf03_power_on(struct lms501kf03 *lcd)
> +{
> + int ret = 0;
> + struct lcd_platform_data *pd;
> +
> + pd = lcd->lcd_pd;
> +
> + if (!pd->power_on) {
> + dev_err(lcd->dev, "power_on is NULL.\n");
> + return -EFAULT;
we may need to do -EINVAL instead of EFAULT as EFAULT tends to be for
the invalid memory addresses.
> + } else {
> + pd->power_on(lcd->ld, 1);
> + msleep(pd->power_on_delay);
> + }
> +
> + if (!pd->reset) {
> + dev_err(lcd->dev, "reset is NULL.\n");
> + return -EFAULT;
may be here too..
> + } else {
> + pd->reset(lcd->ld);
> + msleep(pd->reset_delay);
> + }
> +
> + ret = lms501kf03_ldi_init(lcd);
> + if (ret) {
> + dev_err(lcd->dev, "failed to initialize ldi.\n");
> + return ret;
> + }
> +
> + ret = lms501kf03_ldi_enable(lcd);
> + if (ret) {
> + dev_err(lcd->dev, "failed to enable ldi.\n");
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static int lms501kf03_power_off(struct lms501kf03 *lcd)
> +{
> + int ret = 0;
> + struct lcd_platform_data *pd;
> +
> + pd = lcd->lcd_pd;
> +
> + ret = lms501kf03_ldi_disable(lcd);
> + if (ret) {
> + dev_err(lcd->dev, "lcd setting failed.\n");
> + return -EIO;
> + }
> +
> + msleep(pd->power_off_delay);
> +
> + pd->power_on(lcd->ld, 0);
> +
seems that you are calling the core lcd framework api, i am curious to
know why, :p , and obviously i dunno why its calling that way.
> + return 0;
> +}
> +
> +static int lms501kf03_power(struct lms501kf03 *lcd, int power)
> +{
> + int ret = 0;
> +
> + if (lms501kf03_power_is_on(power) &&
> + !lms501kf03_power_is_on(lcd->power))
> + ret = lms501kf03_power_on(lcd);
> + else if (!lms501kf03_power_is_on(power) &&
> + lms501kf03_power_is_on(lcd->power))
> + ret = lms501kf03_power_off(lcd);
> +
seems that ret is used unitialised in this function bug is covered by
ret = 0 assignment, but why that else case is missed, or i am just
misreading?
> + if (!ret)
> + lcd->power = power;
> +
> + return ret;
> +}
> +
[snip]
> +
> +static int lms501kf03_probe(struct spi_device *spi)
> +{
> + struct lms501kf03 *lcd = NULL;
> + struct lcd_device *ld = NULL;
> + int ret = 0;
> +
> + lcd = devm_kzalloc(&spi->dev, sizeof(struct lms501kf03), GFP_KERNEL);
> + if (!lcd)
> + return -ENOMEM;
> +
glad you used devm api.
> + /* lms501kf03 lcd panel uses 3-wire 9-bit SPI Mode. */
> + spi->bits_per_word = 9;
> +
> + ret = spi_setup(spi);
> + if (ret < 0) {
> + dev_err(&spi->dev, "spi setup failed.\n");
> + return ret;
> + }
> +
> + lcd->spi = spi;
> + lcd->dev = &spi->dev;
> +
> + lcd->lcd_pd = spi->dev.platform_data;
> + if (!lcd->lcd_pd) {
> + dev_err(&spi->dev, "platform data is NULL\n");
> + return -EFAULT;
May be here too -EINVAL or some correct errno should be returned not
the EFAULT no?
> + }
> +
> + ld = lcd_device_register("lms501kf03", &spi->dev, lcd,
> + &lms501kf03_lcd_ops);
> + if (IS_ERR(ld))
> + return PTR_ERR(ld);
> +
> + lcd->ld = ld;
> +
[snip]
> +#if defined(CONFIG_PM)
> +static unsigned int before_power;
> +
> +static int lms501kf03_suspend(struct spi_device *spi, pm_message_t mesg)
> +{
> + int ret = 0;
> + struct lms501kf03 *lcd = dev_get_drvdata(&spi->dev);
> +
> + dev_dbg(&spi->dev, "lcd->power = %d\n", lcd->power);
> +
> + before_power = lcd->power;
> +
> + /*
> + * when lcd panel is suspend, lcd panel becomes off
> + * regardless of status.
> + */
> + ret = lms501kf03_power(lcd, FB_BLANK_POWERDOWN);
> +
returning ret is redundant just like that return that is mentioned
above. you can return as is.
> + return ret;
> +}
> +
> +static int lms501kf03_resume(struct spi_device *spi)
> +{
> + int ret = 0;
> + struct lms501kf03 *lcd = dev_get_drvdata(&spi->dev);
> +
> + lcd->power = FB_BLANK_POWERDOWN;
> +
> + ret = lms501kf03_power(lcd, FB_BLANK_UNBLANK);
> +
> + return ret;
> +}
here too..
> +#else
> +#define lms501kf03_suspend NULL
> +#define lms501kf03_resume NULL
> +#endif
> +
> +void lms501kf03_shutdown(struct spi_device *spi)
> +{
> + struct lms501kf03 *lcd = dev_get_drvdata(&spi->dev);
> +
> + lms501kf03_power(lcd, FB_BLANK_POWERDOWN);
> +}
> +
> +static struct spi_driver lms501kf03_driver = {
> + .driver = {
> + .name = "lms501kf03",
> + .owner = THIS_MODULE,
> + },
> + .probe = lms501kf03_probe,
> + .remove = lms501kf03_remove,
> + .shutdown = lms501kf03_shutdown,
> + .suspend = lms501kf03_suspend,
> + .resume = lms501kf03_resume,
> +};
> +
> +module_spi_driver(lms501kf03_driver);
> +
nice, using module_spi_driver reduce the duplication of the
spi_register unregister code.
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