Re: [PATCH 09/20] regmap: _regmap_raw_write fix for busses without write()

Markus Pargmann
2015-08-12T13:05:26Z

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On Wed, Aug 12, 2015 at 01:34:06PM +0100, Mark Brown wrote:
> On Wed, Aug 12, 2015 at 02:20:11PM +0200, Markus Pargmann wrote:
> > On Wed, Aug 12, 2015 at 12:20:35PM +0100, Mark Brown wrote:
> > > On Wed, Aug 12, 2015 at 12:12:34PM +0200, Markus Pargmann wrote:
> > >
> > > > @@ -1229,6 +1229,11 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
> > > > }
> > > > }
> > > >
> > > > + if (!map->bus->write && val_len == map->format.val_bytes) {
> > > > + ret = _regmap_bus_reg_write(map, reg, *(unsigned int *)val);
> > > > + return ret;
> > > > + }
>
> > > This is broken - you can't use a raw value as a register value. The
>
> > I am not sure what you mean here?
>
> > The register value given to _regmap_raw_write is the real register
> > value, not formatted differenty. This is given directly towards
> > bus->reg_write() which should handle the rest.
>
> I mean the value for the register, not the register address.
>
> > At least that's how I understood the code. For example regmap_read()
> > directly calls _regmap_read() which in turn calls directly
> > bus->reg_read() without any formating.
>
> You're adding this code to regmap_raw_write() which takes raw register
> values for the device, not unsigned integers.

Ah yes, I see.

>
> > > endianness of the device may not be the same as the endianness of the
> > > system and you can't cast a value to unsigned int, the value may be of
> > > any size.
>
> > Yes right. On the other hand if bus->read() and bus->write() was not set
> > in the init method (before this patch series) no formatting functions at
> > all were assigned. So it was always ignored for bus->reg_read() and
> > bus->reg_write()?!
>
> I'm not sure what the "it" you're talking about here is, sorry. There
> are unsupported features in the API especially for cases that don't make
> a huge amount of sense, the error handling isn't always complete. It
> sounds like you might be trying to support one of these nonsensical
> cases - it's not obvious what raw I/O on a device where we don't know
> the raw format of the device should mean or how anything could sensibly
> use that.

The bus and the regmap user are separate. So as a regmap user, I am not
able to know if the bus the device is connected to actually supports raw
reads/writes. At least it should not fail with a null pointer when using
these functions anyway so yes error handling is missing a bit here.

Also the real use of this function is regmap_bulk_write() which always
uses _regmap_raw_write() regardless of a missing bus->write() function.
So regmap_bulk_write will fail for those as well and this should be
supported.

But it is probably better to handle this in regmap_bulk_write() and
add a simple check for bus->write() here.

Best Regards,

Markus

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