Re: [alsa-devel] [PATCH 5/6] mtd: rawnand: ams-delta: use GPIO lookup table

On Sun, May 20, 2018 at 09:27:05PM +0200, Ladislav Michl wrote:

On Sat, May 19, 2018 at 11:55:51PM +0200, Janusz Krzysztofik wrote:

quoted

On Saturday, May 19, 2018 8:00:38 PM CEST Andy Shevchenko wrote:

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On Sat, May 19, 2018 at 2:15 AM, Janusz Krzysztofik [off-list ref] 

wrote:

quoted

quoted

On Friday, May 18, 2018 11:21:14 PM CEST Andy Shevchenko wrote:

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On Sat, May 19, 2018 at 12:09 AM, Janusz Krzysztofik

[off-list ref] wrote:

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+       gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy",
GPIOD_IN);
+       if (!IS_ERR_OR_NULL(gpiod_rdy)) {

So, is it optional or not at the end?
If it is, why do we check for NULL?

As far as I can understand, nand_chip->dev_ready() callback is optional.
That's why I decided to use the _optional variant of devm_gpiod_get(). In
case of ams-delta, the dev_ready() callback depends on availability of
the 'rdy' GPIO pin. As a consequence, I'm checking for both NULL and ERR
in order to decide if dev_ready() will be supported.

I can pretty well replace it with the standard form and check for ERR only
if the purpose of the _optional form is different.

NULL check in practice discards the _optional part of gpiod_get(). So,
either you use non-optional variant and decide how to handle an
errors, or user _optional w/o NULL check.

OK, I'm going to use something like the below while submitting v2:

-	gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy", GPIOD_IN);
-	if (!IS_ERR_OR_NULL(gpiod_rdy)) {
-		this->dev_ready = ams_delta_nand_ready;
-	} else {
-		this->dev_ready = NULL;
-		pr_notice("Couldn't request gpio for Delta NAND ready.\n");
+	priv->gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy",
+						  GPIOD_IN);
+	if (IS_ERR(priv->gpiod_rdy)) {
+		err = PTR_ERR(priv->gpiod_nwp);

??? --------------------------------^^^^^^^^^

quoted

+		dev_warn(&pdev->dev, "RDY GPIO request failed (%d)\n", err);
+		goto err_gpiod;

Driver will just use worst case delay instead of RDY signal, so this
is perhaps too strict. I will work with degraded performance.

If RDY signal is not available then the board should not define it.
Degrading performance and having users wondering because RDY is
sometimes not available is not great. Especially if we get -EPROBE_DEFER
here.

Thanks.

-- 
Dmitry