Re: [PATCH 2/2] maps/mtd-ram: add an of-platform driver

Wolfram Sang
2009-05-21T00:46:43Z

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Hello Grant,

as I am just working on V2 (fixed even some additional things), two more
questions came up:

On Tue, May 19, 2009 at 08:57:15AM -0600, Grant Likely wrote:
> On Wed, Jan 21, 2009 at 11:41 AM, Wolfram Sang <w.sang@pengutronix.de> wrote:
> > Create an of-aware driver using the now exported generic functions from
> > plat-ram.c. A typical oftree snipplet for it looks like this:
> >
> > sram@04e00000 {
> >        compatible = "mtd-ram";
> >        reg = <0x04e00000 0x00200000>;
> >        bank-width = <2>;
> > };
> >
> > Partitions on this device are not yet supported.
>
> This is a new device tree binding. It must be documented in
> Documentation/powerpc/dts-bindings and posted to
> devicetree-discuss@ozlabs.org for review.
>
> > diff --git a/drivers/mtd/maps/Makefile b/drivers/mtd/maps/Makefile
> > index 6d9ba35..f8e3908 100644
> > --- a/drivers/mtd/maps/Makefile
> > +++ b/drivers/mtd/maps/Makefile
> > @@ -58,6 +58,7 @@ obj-$(CONFIG_MTD_WRSBC8260)   += wr_sbc82xx_flash.o
> >  obj-$(CONFIG_MTD_DMV182)       += dmv182.o
> >  obj-$(CONFIG_MTD_SHARP_SL)     += sharpsl-flash.o
> >  obj-$(CONFIG_MTD_PLATRAM)      += plat-ram.o
> > +obj-$(CONFIG_MTD_OFRAM)                += of-ram.o
> >  obj-$(CONFIG_MTD_OMAP_NOR)     += omap_nor.o
> >  obj-$(CONFIG_MTD_INTEL_VR_NOR) += intel_vr_nor.o
> >  obj-$(CONFIG_MTD_BFIN_ASYNC)   += bfin-async-flash.o
> > diff --git a/drivers/mtd/maps/of-ram.c b/drivers/mtd/maps/of-ram.c
> > new file mode 100644
> > index 0000000..4d334a9
> > --- /dev/null
> > +++ b/drivers/mtd/maps/of-ram.c
> > @@ -0,0 +1,120 @@
> > +/*
> > + * drivers/mtd/maps/of-ram.c
> > + *
> > + * Generic of device based RAM map
> > + *
> > + * Copyright (C) 2009 Wolfram Sang, Pengutronix
> > + *
> > + * Using plat-ram.c by Ben Dooks
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms of the GNU General Public License version 2 as published by
> > + * the Free Software Foundation.
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/types.h>
> > +#include <linux/init.h>
> > +#include <linux/kernel.h>
> > +#include <linux/device.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/of_device.h>
> > +#include <linux/of_platform.h>
> > +#include <linux/mtd/plat-ram.h>
> > +
> > +static int of_ram_probe(struct of_device *op, const struct of_device_id *match)
>
> __devinit
>
> > +{
> > +       struct platdata_mtd_ram *pdata;
> > +       struct resource *resource;
> > +       const char *name;
> > +       const u32 *bankwidth;
> > +       int ret = -ENOMEM;
> > +
> > +       pdata = kzalloc(sizeof(*pdata), GFP_KERNEL);
> > +       if (!pdata)
> > +               goto bad0;
> > +       op->dev.platform_data = pdata;
> > +
> > +       name = of_get_property(op->node, "name", NULL);
> > +       if (!name) {
> > +               ret = -ENOENT;
> > +               dev_dbg(&op->dev, "could not get node name\n");
> > +               goto bad1;
> > +       }

Can I just use

name = op->node->name

here? I wonder because of_device in asm/of_device.h states 'node' as "to be
obsoleted". And could I safely assume that all architectures will have the node
entry?

At least, I could drop the error check, if I understand booting-without-of
correctly? A name property will always be constructed, even if it is not
explicitly given.

> > +
> > +       resource = kzalloc(sizeof(struct resource), GFP_KERNEL);
> > +       if (!resource)
> > +               goto bad1;
>
> Why isn't resource on the stack?
>
> > +
> > +       if (of_address_to_resource(op->node, 0, resource)) {
> > +               ret = -ENXIO;
> > +               dev_dbg(&op->dev, "could not create resource\n");
> > +               goto bad2;
> > +       }
> > +
> > +       bankwidth = of_get_property(op->node, "bank-width", NULL);
> > +       if (*bankwidth == 0) {
> > +               ret = -ENOENT;
> > +               dev_dbg(&op->dev, "bank width not set\n");
> > +               goto bad2;
> > +       }
> > +       pdata->bankwidth = *bankwidth;
> > +
> > +       ret = __platram_probe(&op->dev, name, resource, pdata);
> > +       kfree(resource);
> > +
> > +       if (ret)
> > +               goto bad1;
> > +
> > +       return 0;
> > +
> > + bad2:
> > +       kfree(resource);
> > + bad1:
> > +       op->dev.platform_data = NULL;
> > +       kfree(pdata);
> > + bad0:
> > +       return ret;
>
> I'd rather see more meaningful labels. ie "err_kalloc:" and
> "err_platram_probe:".
>
> > +}
> > +
> > +static int of_ram_remove(struct of_device *op)
>
> __devexit
>
> > +{
> > +       int ret;
> > +       struct platdata_mtd_ram *pdata = op->dev.platform_data;
> > +
> > +       ret = __platram_remove(&op->dev);
> > +       op->dev.platform_data = NULL;
> > +       kfree(pdata);
> > +       return ret;
> > +}
> > +
> > +static struct of_device_id of_ram_match[] = {
> > +       { .compatible = "mtd-ram", },
> > +       {},
> > +};
> > +MODULE_DEVICE_TABLE(of, of_ram_match);
> > +
> > +static struct of_platform_driver of_ram_driver = {
>
> __devinitdata

I assume you mean the match_table and not the of_platform_driver. Shouldn't it
even better be const and using __devinitconst?

>
> > +       .owner = THIS_MODULE,
> > +       .name = "of-ram",
>
> This name is too generic for an of_platform device. 'mtd' needs to be
> in there somewhere.
>
> > +       .match_table = of_ram_match,
> > +       .probe = of_ram_probe,
> > +       .remove = of_ram_remove,
>
> __devexit_p()
>
> > +};
> > +
> > +static int __init of_ram_init(void)
> > +{
> > +       return of_register_platform_driver(&of_ram_driver);
> > +}
> > +
> > +static void __exit of_ram_exit(void)
> > +{
> > +       of_unregister_platform_driver(&of_ram_driver);
> > +}
> > +
> > +module_init(of_ram_init);
>
> Put the module_init() statement directly after the of_ram_init() definition.
>
> > +module_exit(of_ram_exit);
> > +
> > +MODULE_AUTHOR("Wolfram Sang");
> > +MODULE_DESCRIPTION("MTD OF RAM map driver");
> > +MODULE_LICENSE("GPL v2");
> > --
> > 1.5.6.5
> >
> > _______________________________________________
> > Linuxppc-dev mailing list
> > Linuxppc-dev@ozlabs.org
> > https://ozlabs.org/mailman/listinfo/linuxppc-dev
> >
>
>
>
> --
> Grant Likely, B.Sc., P.Eng.
> Secret Lab Technologies Ltd.
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

--
Pengutronix e.K. | Wolfram Sang |
Industrial Linux Solutions | http://www.pengutronix.de/ |

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