On Mon, May 21, 2018 at 10:21:46PM +0200, Janusz Krzysztofik wrote:
On Sunday, May 20, 2018 10:08:22 PM CEST Dmitry Torokhov wrote:
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:
On Saturday, May 19, 2018 8:00:38 PM CEST Andy Shevchenko wrote:
On Sat, May 19, 2018 at 2:15 AM, Janusz Krzysztofik jmkrzyszt@gmail.com
wrote:
On Friday, May 18, 2018 11:21:14 PM CEST Andy Shevchenko wrote: > On Sat, May 19, 2018 at 12:09 AM, Janusz Krzysztofik > > jmkrzyszt@gmail.com wrote: > > + 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);??? --------------------------------^^^^^^^^^
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.
Hi,
I'm a bit lost after your comments.
As far as I can read the code of gpiod_get_optional and underlying functions, if a board doesn't define the "rdy" pin in a respective lookup table, the function returns NULL and the device gets a chance to work in degraded mode.
NULL may also happen if the driver probes the device before the lookup table is added. In that case other non-optional pin requests fail with -ENOENT, the probe is deferred and the device gets a chance to probe successfully in late_init if the table is added but fails if not.
If the pin is defined but GPIO device providing that pin is not available (-ENODEV), the probe is initially deferred and may succeed in late_init if the GPIO device appears but fails otherwise.
Isn't that behavior acceptable, close enough to the expected even if not strictly because of that -EPROBE_DEFER?
Yes, this is correct. I was responding to the comment that erroring out in "if (IS_ERR(priv->gpiod_rdy))" branch is too strict. My assertion that it is not. If a board defines RDY pin we should use it and not try to degrade to lower performance mode.
Thanks.