From: Linus Walleij <linus.walleij@linaro.org>
To: Alexandre Courbot <acourbot@nvidia.com>
Cc: linux-arch@vger.kernel.org, gnurou@gmail.com,
Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org,
Grant Likely <grant.likely@secretlab.ca>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 8/9] gpiolib: use gpio_chips list in gpio_to_desc
Date: Tue, 5 Feb 2013 19:01:34 +0100 [thread overview]
Message-ID: <CACRpkdbXvf8mRgpr2MrmcJcT1gTg4mfBOnF8s3=+jS5iAcMtkQ@mail.gmail.com> (raw)
In-Reply-To: <1359822572-26009-10-git-send-email-acourbot@nvidia.com>
On Sat, Feb 2, 2013 at 5:29 PM, Alexandre Courbot <acourbot@nvidia.com> wrote:
> Parse the list of chips to find the descriptor corresponding to a GPIO
> number instead of directly picking the entry of the global gpio_desc[]
> array, which is due to be removed.
>
> This turns the complexity of converting a GPIO number into a descriptor
> from O(1) to O(n) where n is the number of GPIO chips in the system.
> Since n is ought to be small anyway, there should be no noticeable
> performance impact. Moreover, GPIO users who care for speed already have
> implemented their own gpio_get_value() and gpio_set_value() with a
> fast path for the GPIO numbers that matter and this change does not
> affect such use cases.
>
> The descriptor-based GPIO API, due to be introduced soon, will make this
> lookup unnecessary.
>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
OK it's a nice stepping stone.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Yours,
Linus Walleij
WARNING: multiple messages have this Message-ID (diff)
From: Linus Walleij <linus.walleij@linaro.org>
To: Alexandre Courbot <acourbot@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, gnurou@gmail.com
Subject: Re: [PATCH 8/9] gpiolib: use gpio_chips list in gpio_to_desc
Date: Tue, 5 Feb 2013 19:01:34 +0100 [thread overview]
Message-ID: <CACRpkdbXvf8mRgpr2MrmcJcT1gTg4mfBOnF8s3=+jS5iAcMtkQ@mail.gmail.com> (raw)
Message-ID: <20130205180134.ChV_44rqoaLJqKBZC-pHy0LEkYkaTb9z94LiPECrEXI@z> (raw)
In-Reply-To: <1359822572-26009-10-git-send-email-acourbot@nvidia.com>
On Sat, Feb 2, 2013 at 5:29 PM, Alexandre Courbot <acourbot@nvidia.com> wrote:
> Parse the list of chips to find the descriptor corresponding to a GPIO
> number instead of directly picking the entry of the global gpio_desc[]
> array, which is due to be removed.
>
> This turns the complexity of converting a GPIO number into a descriptor
> from O(1) to O(n) where n is the number of GPIO chips in the system.
> Since n is ought to be small anyway, there should be no noticeable
> performance impact. Moreover, GPIO users who care for speed already have
> implemented their own gpio_get_value() and gpio_set_value() with a
> fast path for the GPIO numbers that matter and this change does not
> affect such use cases.
>
> The descriptor-based GPIO API, due to be introduced soon, will make this
> lookup unnecessary.
>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
OK it's a nice stepping stone.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Yours,
Linus Walleij
next prev parent reply other threads:[~2013-02-05 18:01 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-02 16:29 [PATCH 0/9] gpiolib: remove gpio_desc[] static array Alexandre Courbot
2013-02-02 16:29 ` Alexandre Courbot
2013-02-02 16:29 ` [PATCH 1/9] gpiolib: link all gpio_chips using a list Alexandre Courbot
2013-02-02 16:29 ` Alexandre Courbot
2013-02-05 17:00 ` Linus Walleij
2013-02-09 9:20 ` Grant Likely
2013-02-09 9:20 ` Grant Likely
2013-02-02 16:29 ` [PATCH 2/9] gpiolib: use gpio_chips list in gpiolib_sysfs_init Alexandre Courbot
2013-02-02 16:29 ` Alexandre Courbot
2013-02-05 17:04 ` Linus Walleij
2013-02-09 9:22 ` Grant Likely
2013-02-09 9:22 ` Grant Likely
2013-02-02 16:29 ` [PATCH 3/9] gpiolib: use gpio_chips list in gpiochip_find Alexandre Courbot
2013-02-02 16:29 ` Alexandre Courbot
2013-02-05 17:05 ` Linus Walleij
2013-02-09 9:25 ` Grant Likely
2013-02-09 9:25 ` Grant Likely
2013-02-02 16:29 ` [PATCH 4/9] gpiolib: use gpio_chips list in sysfs ops Alexandre Courbot
2013-02-02 16:29 ` Alexandre Courbot
2013-02-05 17:15 ` Linus Walleij
2013-02-05 17:15 ` Linus Walleij
2013-02-09 9:37 ` Grant Likely
2013-02-09 9:37 ` Grant Likely
2013-02-09 13:53 ` Alexandre Courbot
2013-02-02 16:29 ` [PATCH 5/9] gpiolib: use gpio_chips list in gpiochip_find_base Alexandre Courbot
2013-02-02 16:29 ` Alexandre Courbot
2013-02-05 17:21 ` Linus Walleij
2013-02-06 4:48 ` Alex Courbot
2013-02-09 9:47 ` Grant Likely
2013-02-09 9:47 ` Grant Likely
2013-02-02 16:29 ` [PATCH 6/9] gpiolib: use descriptors internally Alexandre Courbot
2013-02-02 16:29 ` Alexandre Courbot
2013-02-05 17:53 ` Linus Walleij
2013-02-07 6:57 ` Alexandre Courbot
2013-02-09 9:17 ` Grant Likely
2013-02-09 9:17 ` Grant Likely
2013-02-11 14:09 ` Linus Walleij
2013-02-11 15:40 ` Paul Mundt
2013-02-11 15:40 ` Paul Mundt
2013-02-11 17:39 ` Stephen Warren
2013-02-12 12:29 ` Linus Walleij
2013-02-12 15:59 ` Paul Mundt
2013-02-12 17:18 ` Arnd Bergmann
2013-02-09 13:11 ` Grant Likely
2013-02-09 13:11 ` Grant Likely
2013-02-09 14:15 ` Alexandre Courbot
2013-02-09 13:24 ` Grant Likely
2013-02-09 13:24 ` Grant Likely
2013-02-09 14:18 ` Alexandre Courbot
2013-02-02 16:29 ` [PATCH 7/9] gpiolib: let gpio_chip reference its descriptors Alexandre Courbot
2013-02-05 18:00 ` Linus Walleij
2013-02-09 13:28 ` Grant Likely
2013-02-02 16:29 ` [PATCH 8/9] gpiolib: use gpio_chips list in gpio_to_desc Alexandre Courbot
2013-02-05 18:01 ` Linus Walleij [this message]
2013-02-05 18:01 ` Linus Walleij
2013-02-09 9:58 ` Grant Likely
2013-02-09 9:58 ` Grant Likely
2013-02-09 14:21 ` Alexandre Courbot
2013-02-09 14:21 ` Alexandre Courbot
2013-02-09 14:37 ` Grant Likely
2013-02-02 16:29 ` [PATCH 9/9] gpiolib: dynamically allocate descriptors array Alexandre Courbot
2013-02-02 16:29 ` Alexandre Courbot
2013-02-05 18:02 ` Linus Walleij
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