Messages in this thread |  | | Date | Mon, 2 Dec 2013 19:50:41 +0900 | From | Alex Courbot <> | Subject | Re: [PATCH] gpio: better lookup method for platform GPIOs |
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On 11/29/2013 12:54 AM, Andy Shevchenko wrote: > On Thu, Nov 28, 2013 at 10:46 AM, Alexandre Courbot <acourbot@nvidia.com> wrote: >> Change the format of the platform GPIO lookup tables to make them less >> confusing and improve lookup efficiency. >> >> The previous format was a single linked-list that required to compare >> the device name and function ID of every single GPIO defined for each >> lookup. Switch that to a list of per-device tables, so that the lookup >> can be done in two steps, omitting the GPIOs that are not relevant for a >> particular device. >> >> The matching rules are now defined as follows: >> - The device name must match *exactly*, and can be NULL for GPIOs not >> assigned to a particular device, >> - If the function ID in the lookup table is NULL, the con_id argument of >> gpiod_get() will not be used for lookup. However, if it is defined, it >> must match exactly. >> - The index must always match. > > Thanks for that, since I'm also was a bit confused of those dev_id/con_id stuff. > Few comments below (mostly about style). > > >> --- a/Documentation/gpio/board.txt >> +++ b/Documentation/gpio/board.txt > >> @@ -88,16 +89,20 @@ Note that GPIO_LOOKUP() is just a shortcut to GPIO_LOOKUP_IDX() where idx = 0. >> >> A lookup table can then be defined as follows: >> >> - struct gpiod_lookup gpios_table[] = { >> - GPIO_LOOKUP_IDX("gpio.0", 15, "foo.0", "led", 0, GPIO_ACTIVE_HIGH), >> - GPIO_LOOKUP_IDX("gpio.0", 16, "foo.0", "led", 1, GPIO_ACTIVE_HIGH), >> - GPIO_LOOKUP_IDX("gpio.0", 17, "foo.0", "led", 2, GPIO_ACTIVE_HIGH), >> - GPIO_LOOKUP("gpio.0", 1, "foo.0", "power", GPIO_ACTIVE_LOW), >> - }; >> +struct gpiod_lookup_table gpios_table = { >> + .dev_id = "foo.0", >> + .size = 4, >> + .table = { >> + GPIO_LOOKUP_IDX("gpio.0", 15, "led", 0, GPIO_ACTIVE_HIGH), >> + GPIO_LOOKUP_IDX("gpio.0", 16, "led", 1, GPIO_ACTIVE_HIGH), >> + GPIO_LOOKUP_IDX("gpio.0", 17, "led", 2, GPIO_ACTIVE_HIGH), >> + GPIO_LOOKUP("gpio.0", 1, "power", GPIO_ACTIVE_LOW), > > Can you use deeper indentation for GPIO_* lines here?
Fixed.
>> --- a/drivers/gpio/gpiolib.c >> +++ b/drivers/gpio/gpiolib.c > >> @@ -2326,72 +2322,77 @@ static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id, >> return desc; >> } >> >> -static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id, >> - unsigned int idx, >> - enum gpio_lookup_flags *flags) >> +static struct gpiod_lookup_table *gpiod_find_lookup_table(struct device *dev) >> { >> const char *dev_id = dev ? dev_name(dev) : NULL; >> - struct gpio_desc *desc = ERR_PTR(-ENODEV); >> - unsigned int match, best = 0; >> - struct gpiod_lookup *p; >> + struct gpiod_lookup_table *table; >> >> mutex_lock(&gpio_lookup_lock); >> >> - list_for_each_entry(p, &gpio_lookup_list, list) { >> - match = 0; >> + list_for_each_entry(table, &gpio_lookup_list, list) { >> + if (table->dev_id && dev_id && strcmp(table->dev_id, dev_id)) > > Maybe check !dev_id outside of loop?
And create two loops, one for each case? Might complicate the code for little benefit IMHO, but please elaborate if I missed your point.
> >> + continue; >> >> - if (p->dev_id) { >> - if (!dev_id || strcmp(p->dev_id, dev_id)) >> - continue; >> + if (dev_id != table->dev_id) >> + continue; >> >> - match += 2; >> - } >> + return table; > > What about > > if (dev_id == table->dev_id) > return table; > > ?
Actually my algorithm is broken to start with - and dangerous, as the missed mutex_unlock() you spotted later testifies. I will rewrite it in a (hopefully) sounder way.
>> +static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id, >> + unsigned int idx, >> + enum gpio_lookup_flags *flags) >> +{ >> + struct gpio_desc *desc = ERR_PTR(-ENODEV); >> + struct gpiod_lookup_table *table; >> + int i; >> >> - if (match > best) { >> - struct gpio_chip *chip; >> > > Looks like redundant empty line.
Fixed.
> >> - chip = find_chip_by_name(p->chip_label); >> + table = gpiod_find_lookup_table(dev); >> + if (!table) >> + return desc; >> >> - if (!chip) { >> - dev_warn(dev, "cannot find GPIO chip %s\n", >> - p->chip_label); >> - continue; >> - } >> + for (i = 0; i < table->size; i++) { >> + struct gpio_chip *chip; >> + struct gpiod_lookup *p = &table->table[i]; >> >> - if (chip->ngpio <= p->chip_hwnum) { >> - dev_warn(dev, "GPIO chip %s has %d GPIOs\n", >> - chip->label, chip->ngpio); >> + if (p->idx != idx) >> + continue; >> + >> + if (p->con_id) { >> + if (!con_id || strcmp(p->con_id, con_id)) > > Could be one 'if' and moreover !con_id check might be outside a loop.
Again, wouldn't that require two separate loops?
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