Hi Trilok, > Hi Arun, > > On Fri, Oct 1, 2010 at 8:55 AM, Arun MURTHY > <arun.murthy@xxxxxxxxxxxxxx> wrote: > > Hi Trilok, > > > >> Hi Arun, > >> > >> Adding Bill Gatliff (anyway, CC list already crowded) > >> > >> On Wed, Sep 29, 2010 at 10:19 AM, Arun MURTHY > >> <arun.murthy@xxxxxxxxxxxxxx> wrote: > >> >> Arun MURTHY wrote: > >> >> >>>> Shouldn't PWM_DEVICES select HAVE_PWM? > >> >> >>> > >> >> >>> No not required, the entire concept is to remove HAVE_PWM and > >> use > >> >> >> PWM_CORE. > >> > >> There is already nice and clean framework written by Bill for PWM, > if > >> you grep the LKML and linux-embedded mailing list archive then you > >> will get his patches, and it seems that he had promised to send the > >> updated version few week back, but not heard from him (may be > because > >> he was travelling as per FB status). > >> > >> Please evaluate that framework too. > >> > > Thanks for this information, I did search in linux-embedded mailing > list > > archive. Below are my views on that patch set. > > Many of the functions that has been defined in pwm core driver > > written by Bill Gatliff is not being used by the most of the pwm > drivers > > except Atmel PWM driver. I rather felt the pwm core driver was an > attempt > > made to generalize the Atmel pwm driver. > > And moreover this was posted long back somewhere in the beginning of > this > > year i.e Feb and the thread is dead thereafter. > > > > This patch has been submitted focusing all the existing pwm drivers > and > > only these are the functions that are being used by pwm drivers. > > This patch set also included patch to align all the existing pwm > driver > > with the pwm core driver. > > So it is an attempt to generalize most of the pwm drivers and > > conclude with a pwm core driver. > > I don't agree that Bill had only atmel drivers view. The PWM framework > was discussed in-depth and at that time reviewers also requested once > to provide more example drivers using these drivers, someone said "we > atleast need three drivers as rule of thumb". Let's wait until Bill > reviews your framework, I am sure we don't need to end up the same > problems faced by Bill while designing that framework in your code > too. > You can have a look at the pwm_config_nosleep(),pwm_set_polarity(), pwm_synchronize(),pwm_unsynchronize(), pwm_set_handler() etc. These are not being used by the exsting pwm drivers except Atmel pwm. I mean not the functions but the functionality. PWM is a simple device and most of its clients are controlling intensity of backlight, leds, vibrator etc. I don't think these complex functionality are required. And moreover it also refers to GPIO pins, in that case it comes under a different classification. The one that I have suggested is a generic pwm core driver. You can have a look at the existing pwm drivers in drivers/mfd/twl6030-pwm.c, arch/arm/plat-samsung/pwm.c, arch/arm/plat-mxc/pwm.c, arch/arm/plat-pxa/pwm.c, arch/mips/jz4740/pwm.c. None of these include the function provided the patch " [PWM PATCH 1/5] API to consolidate PWM devices behind a common user and kernel interface " except pwm_enable, pwm_config, pwm_disable. I have focused on all these and come up with this design. And moreover Bill's patch set for pwm core driver, becomes incompatible with pwm based backlight and led driver(drivers/leds/leds-pwm.c, drivers/video/backlight/pwm_bl.c) and drivers/input/misc/pwm-beeper.c. I don't mind waiting for Bill's review on my patch, but he is not active since Feb 2010. Thanks and Regards, Arun R Murthy -------------
