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Date: Mon, 07 Mar 2011 08:00:34 +0100 From: Lars-Peter Clausen <lars@...afoo.de> To: Kukjin Kim <kgene.kim@...sung.com> CC: 'Ben Dooks' <ben-linux@...ff.org>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 08/09] ARM: s3c2440: gta02: Request usb pullup pin before using it On 03/07/2011 07:42 AM, Kukjin Kim wrote: > Lars-Peter Clausen wrote: >> >> On 02/28/2011 11:44 AM, Kukjin Kim wrote: >>> Lars-Peter Clausen wrote: >>>> >>>> On 02/28/2011 07:16 AM, Kukjin Kim wrote: >>>>> Lars-Peter Clausen wrote: >>>>>> >>>>>> Request the gpio pin used to control the usb pullup before using it > to >>>>> avoid >>>>>> a >>>>>> runtime warning about an auto-requested gpio. >>>>>> >>>>>> Signed-off-by: Lars-Peter Clausen <lars@...afoo.de> >>>>>> --- >>>>>> arch/arm/mach-s3c2440/mach-gta02.c | 17 +++++++++++++++-- >>>>>> 1 files changed, 15 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/arch/arm/mach-s3c2440/mach-gta02.c >>>>> b/arch/arm/mach-s3c2440/mach- >>>>>> gta02.c >>>>>> index 1396639..94456fa 100644 >>>>>> --- a/arch/arm/mach-s3c2440/mach-gta02.c >>>>>> +++ b/arch/arm/mach-s3c2440/mach-gta02.c >>>>>> @@ -451,11 +451,11 @@ static void gta02_udc_command(enum >>> s3c2410_udc_cmd_e >>>>>> cmd) >>>>>> switch (cmd) { >>>>>> case S3C2410_UDC_P_ENABLE: >>>>>> pr_debug("%s S3C2410_UDC_P_ENABLE\n", __func__); >>>>>> - gpio_direction_output(GTA02_GPIO_USB_PULLUP, 1); >>>>>> + gpio_set_value(GTA02_GPIO_USB_PULLUP, 1); >>>>> >>>>> How about following instead? >>>>> gpio_request(GTA02_GPIO_USB_PULLUP, "USB_PULLUP"); >>>>> gpio_direction_output(GTA02_GPIO_USB_PULLUP, 1); >>>>> gpio_free(GTA02_GPIO_USB_PULLUP); >>>>> >>>> >>>> I don't think that is a good idea. This gpio should really be reserved > for >>>> the >>>> udc driver. If it is freed again, it could be requested from someone > else >>>> which >>>> could lead to undefined behaviour. >>>> >>> Yes right, but I mean the board designer already knows the usage of >>> regarding GPIOs on his board. >>> So why do we really need gpio_request for it?... >> >> Well, for one because it's part of the gpio-api. You should not call any >> other >> gpio functions on a pin unless you've successfully requested that pin. >> On the other hand this helps debugging and ensures that the same gpio is > not >> used by two drivers accident. For example it is also possible to request >> gpios >> from userspace using the gpio sysfs. So by keeping the gpio requested it > wont >> be possible to request it from userspace by accident. And the gpio will > also >> be >> listed in the gpio debugfs file, which can be helpful for debugging as > well. >> >> - Lars > > Hi Lars, > > Ok, will apply :) > Thanks. > > Best regards, > Kgene. > -- > Kukjin Kim <kgene.kim@...sung.com>, Senior Engineer, > SW Solution Development Team, Samsung Electronics Co., Ltd. > Hi Kgene Actually I've prepared another patch, which I'm was about to send in a few minutes, which moves the controlling of the pullup pin to the udc driver. - Lars -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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