Re: [PATCH 5/7] Add MCI card support to barebox

[Juergen Beisert <jbe@pengutronix.de>]

Sascha Hauer wrote:
> On Thu, Oct 07, 2010 at 03:24:16PM +0200, Juergen Beisert wrote:
> > This adds the basic framework to handle MCI cards in barebox.
> >
> > Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
> > ---
> >  drivers/Kconfig        |    1 +
> >  drivers/Makefile       |    1 +
> >  drivers/mci/Kconfig    |   30 ++
> >  drivers/mci/Makefile   |    1 +
> >  drivers/mci/mci-core.c | 1308
> > ++++++++++++++++++++++++++++++++++++++++++++++++ include/mci.h          |
> >  230 +++++++++
> >  6 files changed, 1571 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/mci/Kconfig
> >  create mode 100644 drivers/mci/Makefile
> >  create mode 100644 drivers/mci/mci-core.c
> >  create mode 100644 include/mci.h
>
> This whole patch looks quite good.
> Please add some linebreaks in mci-core.c. I don't want strict 80
> character lines, but some lines are really long.
>
> [snip]
>
> > +static int mci_probe(struct device_d *mci_dev)
> > +{
> > +	struct mci *mci;
> > +	int rc;
> > +
> > +	mci = xzalloc(sizeof(struct mci));
> > +	mci_dev->priv = mci;
> > +
> > +#ifdef CONFIG_MCI_STARTUP
> > +	/* if enabled, probe the attached card immediately */
> > +	rc = mci_card_probe(mci_dev);
> > +	if (rc == -ENODEV) {
> > +		/*
> > +		 * If it fails, add the 'probe' parameter to give the user
> > +		 * a chance to insert a card and try again. Note: This may fail
> > +		 * systems that rely on the MCI card for startup (for the
> > +		 * persistant environment for example)
> > +		 */
> > +		rc = add_mci_parameter(mci_dev);
> > +		if (rc != 0) {
> > +			pr_err("Failed to add 'probe' parameter to the MCI device\n");
> > +			goto on_error;
> > +		}
> > +	}
> > +#endif
> > +
> > +#ifndef CONFIG_MCI_STARTUP
>
> #else instead?
>
> > +	/* add params on demand */
> > +	rc = add_mci_parameter(mci_dev);
> > +	if (rc != 0) {
> > +		pr_err("Failed to add 'probe' parameter to the MCI device\n");
> > +		goto on_error;
> > +	}
> > +#endif
> > +
> > +	return rc;
> > +
> > +on_error:
> > +	free(mci);
> > +	return rc;
> > +}
> > +
>
> [snip]
>
> > +
> > +/** host information */
> > +struct mci_platformdata {
> > +	struct device_d *hw_dev;	/**< the host MCI hardware device */
> > +	unsigned voltages;
> > +	unsigned host_caps;	/**< Host's interface capabilities, refer MMC_VDD_*
> > and FIXME */ +	unsigned f_min;		/**< host interface lower limit */
> > +	unsigned f_max;		/**< host interface upper limit */
> > +	unsigned clock;		/**< Current clock used to talk to the card */
> > +	unsigned bus_width;	/**< used data bus width to the card */
> > +
> > +	int (*init)(struct device_d*, struct device_d*);	/**< init the host
> > interface */ +	void (*set_ios)(struct device_d*, struct device_d*,
> > unsigned, unsigned);	/**< change host interface settings */ +	int
> > (*send_cmd)(struct device_d*, struct mci_cmd*, struct mci_data*);	/**<
> > handle a command */ +};
>
> I prefer this struct named mci_host, this seems to match better what it
> actually is.

Hmm, no, its not a "host". It is the MMC/SD card instance. The host is more 
the interface, isn't it (at least for me)?

> For the convenience of drivers set init/set_ios/send_cmd 
> functions should be passed a pointer to the mci_host, not the device,
> because that's what they actually registered. I already prepared a patch
> for this, I'll send it in a seperate mail.

I tried to layering the devices:

 disk_device -> knows how to handle disk drives and partition tables
    |
 mci_device -> knows how to probe and manage MMC/SD cards
    |
 hw_device -> knows how to transfer data

Most functions in the hw_device layer do not need access to any other 
structure data than their own device (okay, there is a exception). So, I 
tried to keep it simple.

jbe

-- 
Pengutronix e.K.                              | Juergen Beisert             |
Linux Solutions for Science and Industry      | Phone: +49-8766-939 228     |
Vertretung Sued/Muenchen, Germany             | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686              | http://www.pengutronix.de/  |

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