From: ryan@bluewatersys•com (Ryan Mallon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 1/7] pwm: Add pwm core driver
Date: Wed, 29 Sep 2010 08:42:05 +1300 [thread overview]
Message-ID: <4CA2450D.8090104@bluewatersys.com> (raw)
In-Reply-To: <1285659648-21409-2-git-send-email-arun.murthy@stericsson.com>
On 09/28/2010 08:40 PM, Arun Murthy wrote:
> The existing pwm based led and backlight driver makes use of the
> pwm(include/linux/pwm.h). So all the board specific pwm drivers will
> be exposing the same set of function name as in include/linux/pwm.h.
> As a result build fails.
>
> In order to overcome this issue all the pwm drivers must register to
> some core pwm driver with function pointers for pwm operations (i.e
> pwm_config, pwm_enable, pwm_disable).
The other major benefit of this patch set is that it allows non-soc
pwms, such as those provided on an i2c or spi device, to be added easily.
> The clients of pwm device will have to call pwm_request, wherein
> they will get the pointer to struct pwm_ops. This structure include
> function pointers for pwm_config, pwm_enable and pwm_disable.
>
> Signed-off-by: Arun Murthy <arun.murthy@stericsson•com>
> Acked-by: Linus Walleij <linus.walleij@stericsson•com>
> ---
> +menuconfig PWM_DEVICES
> + bool "PWM devices"
> + default y
> + ---help---
> + Say Y here to get to see options for device drivers from various
> + different categories. This option alone does not add any kernel code.
This help text doesn't really explain what the option does.
> +struct pwm_device {
> + struct pwm_ops *pops;
> + int pwm_id;
> +};
> +
> +struct pwm_dev_info {
> + struct pwm_device *pwm_dev;
> + struct list_head list;
> +};
These two structures can be merged into one which will make the code
much simpler.
> +static struct pwm_dev_info *di;
This appears to be used as just a list, and could be replaced by:
static LIST_HEAD(pwm_list);
> +struct pwm_device *pwm_request(int pwm_id, const char *name)
> +{
> + struct pwm_dev_info *pwm;
> + struct list_head *pos;
> +
> + down_read(&pwm_list_lock);
> + list_for_each(pos, &di->list) {
> + pwm = list_entry(pos, struct pwm_dev_info, list);
> + if ((!strcmp(pwm->pwm_dev->pops->name, name)) &&
> + (pwm->pwm_dev->pwm_id == pwm_id)) {
> + up_read(&pwm_list_lock);
> + return pwm->pwm_dev;
> + }
> + }
> + up_read(&pwm_list_lock);
> + return ERR_PTR(-ENOENT);
> +}
Is it by design that multiple users can request and use the same pwm or
should pwms have a use count and return -EBUSY if already requested?
> +static int __init pwm_init(void)
> +{
> + struct pwm_dev_info *pwm;
> +
> + pwm = kzalloc(sizeof(struct pwm_dev_info), GFP_KERNEL);
> + if (!pwm)
> + return -ENOMEM;
> + INIT_LIST_HEAD(&pwm->list);
> + di = pwm;
> + return 0;
If di is changed to a list as suggested above this function does not
need to exist.
> +static void __exit pwm_exit(void)
> +{
> + kfree(di);
Do you need to ensure the list is empty first or do module dependencies
ensure that?
~Ryan
--
Bluewater Systems Ltd - ARM Technology Solution Centre
Ryan Mallon 5 Amuri Park, 404 Barbadoes St
ryan at bluewatersys.com PO Box 13 889, Christchurch 8013
http://www.bluewatersys.com New Zealand
Phone: +64 3 3779127 Freecall: Australia 1800 148 751
Fax: +64 3 3779135 USA 1800 261 2934
next prev parent reply other threads:[~2010-09-28 19:42 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-28 7:40 [PATCHv2 0/7] PWM core driver for pwm based led and backlight driver Arun Murthy
2010-09-28 7:40 ` [PATCH 1/7] pwm: Add pwm core driver Arun Murthy
2010-09-28 8:14 ` Vasily Khoruzhick
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FA8F@EXDCVYMBSTM006.EQ1STM.local>
2010-09-28 8:47 ` Vasily Khoruzhick
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FA8F@EXDCVYMBSTM006.EQ1STM.loca l>
2010-09-28 8:50 ` Hemanth V
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FB21@EXDCVYMBSTM006.EQ1STM.local>
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FB21@EXDCVYMBSTM006.EQ1STM.loca l>
2010-09-28 9:34 ` Hemanth V
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FBF9@EXDCVYMBSTM006.EQ1STM.local>
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FBF9@EXDCVYMBSTM006.EQ1STM.loca l>
2010-09-28 10:41 ` Hemanth V
2010-09-28 8:54 ` Lars-Peter Clausen
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FB6B@EXDCVYMBSTM006.EQ1STM.local>
2010-09-28 9:57 ` Lars-Peter Clausen
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FC60@EXDCVYMBSTM006.EQ1STM.local>
2010-09-28 21:04 ` Lars-Peter Clausen
2010-09-29 4:49 ` Arun MURTHY
2010-09-29 12:12 ` Trilok Soni
2010-10-01 3:25 ` Arun MURTHY
2010-10-01 6:47 ` Trilok Soni
2010-10-01 7:25 ` Arun MURTHY
2010-10-01 7:42 ` Jassi Brar
2010-10-01 8:46 ` Arun MURTHY
2010-10-01 10:39 ` Jassi Brar
2010-10-01 18:00 ` Mark Brown
2010-10-04 4:22 ` Arun MURTHY
2010-09-28 17:46 ` Mark Brown
2010-09-28 19:42 ` Ryan Mallon [this message]
2010-09-28 7:40 ` [PATCH 2/7] backlight:pwm: add an element 'name' to platform data Arun Murthy
2010-09-28 17:47 ` Mark Brown
2010-09-28 7:40 ` [PATCH 3/7] leds: pwm: add a new " Arun Murthy
2010-09-28 8:01 ` Eric Miao
2010-09-28 8:36 ` Arun MURTHY
2010-09-28 7:40 ` [PATCH 4/7] pwm: Align existing pwm drivers with pwm-core driver Arun Murthy
2010-09-28 8:58 ` Lars-Peter Clausen
[not found] ` <F45880696056844FA6A73F415B568C69532DC2FB98@EXDCVYMBSTM006.EQ1STM.local>
2010-09-28 10:10 ` Lars-Peter Clausen
2010-09-28 7:40 ` [PATCH 5/7] platform: Update the pwm based led and backlight platform data Arun Murthy
2010-09-28 7:40 ` [PATCH 7/7] pwm: Modify backlight and led Kconfig aligning to pwm core Arun Murthy
[not found] ` <1285659648-21409-7-git-send-email-arun.murthy@stericsson.com>
2010-09-28 8:02 ` [PATCH 6/7] pwm: move existing pwm driver to drivers/pwm Eric Miao
-- strict thread matches above, loose matches on Subject: below --
2010-09-28 10:35 [PATCH 0/7] PWM core driver for pwm based led and backlight driver Arun Murthy
2010-09-28 10:35 ` [PATCH 1/7] pwm: Add pwm core driver Arun Murthy
2010-09-28 12:53 ` Hemanth V
2010-09-28 13:06 ` Samuel Ortiz
2010-09-28 13:35 ` Felipe Balbi
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