[linux-sunxi] Re: [PATCH 3/6] mfd: axp20x: Add support for RSB based AXP223 PMIC

On Mon, Oct 19, 2015 at 2:02 PM, Maxime Ripard
[off-list ref] wrote:

On Fri, Oct 16, 2015 at 02:46:23PM +0800, Chen-Yu Tsai wrote:

quoted

On Fri, Oct 16, 2015 at 2:41 PM, Maxime Ripard
[off-list ref] wrote:

quoted

On Thu, Oct 15, 2015 at 12:32:19AM +0800, Chen-Yu Tsai wrote:

quoted

The AXP223 is a new PMIC commonly paired with Allwinner A23/A33 SoCs.
It is functionally identical to AXP221; only the regulator default
voltage/status and the external host interface are different.

Signed-off-by: Chen-Yu Tsai <redacted>
---
 drivers/mfd/Kconfig        | 12 ++++++
 drivers/mfd/Makefile       |  1 +
 drivers/mfd/axp20x-core.c  |  2 +
 drivers/mfd/axp20x-rsb.c   | 93 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mfd/axp20x.h |  1 +
 5 files changed, 109 insertions(+)
 create mode 100644 drivers/mfd/axp20x-rsb.c

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 9ba3feb3f2fc..6e5edb61d42e 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig

@@ -84,6 +84,7 @@ config MFD_BCM590XX
 config MFD_AXP20X
      bool "X-Powers AXP series PMICs"
      select MFD_AXP20X_I2C
+     select MFD_AXP20X_RSB

 config MFD_AXP20X_CORE
      bool

@@ -102,6 +103,17 @@ config MFD_AXP20X_I2C
        components like regulators or the PEK (Power Enable Key) under the
        corresponding menus.

+config MFD_AXP20X_RSB
+     bool "X-Powers AXP series RSB PMICs"
+     select MFD_AXP20X_CORE
+     depends on SUNXI_RSB=y

Do we need that? Even if the bus is compiled as a module, the driver
will not be probed before that, will it?

There's a compile/link dependency on the __devm_regmap_init_sunxi_rsb().

If it's exported, everything should be fine, no?

quoted

And both drivers are bool, i.e. can't be compiled as a module. What we
don't want is enabling MFD_AXP20X_RSB without SUNXI_RSB.

What would really be the issue here? The driver wouldn't be probed,
and that's it. Or am I missing something?

The RSB bus / slave device functions have been merged into the RSB driver
itself. Enabling MFD_AXP20X_RSB without enabling SUNXI_RSB means that RSB
bus/device related functions are not compiled, i.e. link error:

drivers/built-in.o: In function `axp20x_rsb_probe':
/home/wens/sunxi/linux/drivers/mfd/axp20x-rsb.c:64: undefined
reference to `__devm_regmap_init_sunxi_rsb'
drivers/built-in.o: In function `axp20x_rsb_driver_init':
/home/wens/sunxi/linux/drivers/mfd/axp20x-rsb.c:89: undefined
reference to `sunxi_rsb_driver_register'
Makefile:927: recipe for target 'vmlinux' failed

The dependency is like "depends on I2C=y" for the I2C version.

If you're asking about why "=y", I guess it's because MFD_AXP20X_RSB is bool,
and if the depended on symbol is a tristate, which it actually is for I2c,
we'd want it to be compiled in, and not built as a module, or again we'd get
a undefined reference link error.

Would it make sense to have SUNXI_RSB as a tristate symbol, i.e. can be built
as a module? I'm nore sure. For multi-platform kernels, probably? Currently it
isn't.

Hope this clears it up.


Regards
ChenYu