Re: Using regmap_update_bits to update a write only register

[Lars-Peter Clausen]

On 03/06/2015 08:48 PM, Daniel Baluta wrote:
> On Fri, Mar 6, 2015 at 7:36 PM, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
> > On 03/06/2015 06:26 PM, Daniel Baluta wrote:
> > [...]
> > > I can reproduce the problem with:
> > >
> > > static struct reg_default xxx_reg_defaults[] = {
> > >           { XXX_REG_CTRL0,  0x00 },
> > >           { XXX_REG_CTRL1,  0x00 },
> > >           { XXX_REG_STATUS, 0x00 },
> > > };
> > >
> > > but, not if the reg default definition is:
> > >
> > > static struct reg_default xxx_reg_defaults[] = {
> > >           { XXX_REG_STATUS, 0x00 },
> > >           { XXX_REG_CTRL0,  0x00 },
> > >           { XXX_REG_CTRL1,  0x00 },
> > >     };
> > >
> > > Is this normal?
> >
> >
> > That's a rhetorical question, right?
> >
> > It might be that there is a bug when growing a rbblock to the left. It
> > probably went unnoticed because everybody has their reg defaults ordered in
> > ascending order.
> >
> > Try to put a few debug printks into regcache_rbtree_write() and
> > regcache_rbtree_insert_to_block() to see what exactly is going on when a new
> > register is inserted into the block. How do base_reg and top_reg change.
>
> I cannot test is right now because I don't have access to the physical device.
> Is there a way to use to test the regmap API without an I2C/SPI device?

I did some quick testing today, and the resizing the present bitmap 
definitely broken with the current code. Patch will follow shortly.

- Lars

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