Re: [PATCH v3 1/3] input: pm8xxx-vib: refactor to easily support new SPMI vibrator

From: Fenglin Wu
Date: Thu Jul 27 2023 - 03:51:40 EST




On 7/27/2023 3:07 PM, Krzysztof Kozlowski wrote:
On 25/07/2023 08:16, Fenglin Wu wrote:
-static const struct pm8xxx_regs pm8058_regs = {
- .drv_addr = 0x4A,
- .drv_mask = 0xf8,
- .drv_shift = 3,
- .drv_en_manual_mask = 0xfc,
+static struct reg_field ssbi_vib_regs[VIB_MAX_REG] = {

Change from const to non-const is wrong. How do you support multiple
devices? No, this is way too fragile now.


The register definition is no longer used as the match data, hw_type is
used.

The last suggestion was getting the register base address from the DT
and it has to be added into the offset of SPMI vibrator registers
(either in the previous hard-coded format or the later the reg_filed
data structure), so it's not appropriated to make it constant.

I don't understand this question: "How do you support multiple devices?"
For SSBI vibrator, since all the registers are fixed, and I would assume
that there is no chance to support multiple vibrator devices on the same
SSBI bus. If they are not on the same bus, the regmap device will be
different while the registers definition is the same, and we are still
able to support multiple devices, right?

No, you have static memory. One device probes and changes static memory
to reg+=base1. Second device probes and changes the same to reg+=base2.

Thanks, got it. I can update it with following 2 options:

1) keep the register definition in 'reg_filed' data structure and make it constant, copy it to a dynamically allocated memory before adding the 'reg_base' to the '.reg' variable.

2) Define the register offsets as constant data and add the 'reg_base' to the 'reg' while using 'regmap_read()'/'regmap_write()' functions.

which one is the preferred way?


The similar story for SPMI vibrators and it can support multiple devices
if they are located on different SPMI bus, or even if they are on the
same SPMI bus but just having different SID or PID.

Sorry, such code cannot go in. These must stay const and you must write
driver without any static allocations or singleton-like patterns.


Best regards,
Krzysztof