Messages in this thread | | | From | Michael Buesch <> | Subject | Re: [PATCH v2] Add GPIO-based MMC/SD driver | Date | Mon, 21 Jul 2008 23:21:59 +0200 |
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On Monday 21 July 2008 22:41:35 David Brownell wrote: > So what this driver adds is mostly a userspace interface, yes?
Mostly. It also provides a simple platform device.
> If so, please refocus the descriptions a bit more on that; > it's not actually a "GPIO based MMC/SD driver"; it's really > a "Configfs creation interface for GPIO based MMC/SD". > > > > > + res = sscanf(buf, "%" GPIOMMC_MAX_NAMELEN_STR "s %u %u %u %u %u %u %u %u", > > Kind of ugly, yes? ;)
This is already gone.
> Please switch to the more conventional "MOSI" (Master Out, Slave In) > and "MISO" (Master In, Slave Out). That's unambiguous. If you want > to be a bit more clear you could say that MOSI goes to the MMC/SD > card pin 2 (card data in), and MISO goes to MMC/SD card pin 7 (card > data out).
Maybe.
> > > + if (res < 8) > > > + pdata->p.no_spi_delay = 0; /* Default: Delay turned on */ > > > + if (res < 7) > > > + pdata->p.max_bus_speed = 5000000; /* Default: 5Mhz */ >
> So I'd default to leaving the delay off
How to?
> > > + if (res < 6) > > > + pdata->p.mode = 0; /* Default: SPI mode 0 */ > > Don't need to do this. The mmc_spi driver forces mode 0 in > any case...
Where's that documented?
> > > +config GPIOMMC > > > + tristate "MMC/SD over GPIO-based SPI" > > "Sysfs interface for ..." > > Because we can already do MMC/SD over GPIO-SPI, > without using this code.
This also adds a platform device interface for convenience (as it also uses that internally).
> > > +config MMC_S3C > > > + tristate "Samsung S3C SD/MMC Card Interface support" > > > + depends on ARCH_S3C2410 && MMC > > MMC_S3C doesn't belong in this patch...
Yeah that was a mismerge. You are commenting on an obsolete patch.
> > > + * @no_spi_delay: Do not use delays in the lowlevel SPI bitbanging code. > > > + * This is not standards compliant, but may be required for some > > > + * embedded machines to gain reasonable speed. > > Rather than emphasize "not standards compliant", I'd instead emphasize that > bitbanged SPI is so slow that you probably don't want to slow it down any > more by additional delays between per-bit operations!
I'd say you cannot tell how fast the GPIOs are. They can be pretty fast on a huge machine.
> Again, please don't promote a *SECOND* platform-device based mechanism
It is not a second mechanism, it is a mechanism on top of the first two mechanisms.
> > > +Registering devices via platform-device > > > +======================================= > > > + > > > +The platform-device interface is used for registering MMC/SD devices that are > > > +part of the hardware platform. This is most useful only for embedded machines > > > +with MMC/SD devices statically connected to the platform GPIO bus. > > There is no "platform GPIO bus" ...
hm??
> This is the interface I'd rather just not see exposed ...
People asked me to expose it. It was hidden in the first patch that I submitted. I'm not going to change this just to see the next one yelling "I want to see this interface in public" again.
> > > +Registering devices via sysfs > > > +============================= > > This is the interface I don't have any particular issues with.
Yeah, but it's gone. See updated patches.
-- Greetings Michael.
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