gpio: 74x164: use a compatible fallback and don't extend the driver

From: Bartosz Golaszewski <[email protected]>

This reverts commit b1468db9d865deb5271c9a20d05201b1c0636895.

There's no need to add a new compatible to the driver code, we can handle it with a DT fallback.

Signed-off-by Bartosz Golaszewski <[email protected]>

---

From: Bartosz Golaszewski <[email protected]>

This model is 1:1 compatible with fairchild,74hc595 so use the latter as a fallback instead of adding a new stand-alone compatible.

Fixes 0ba6cec7acbb ("dt-bindings: gpio: fairchild,74hc595: Add On Semi MC74HC595A compat")

Signed-off-by Bartosz Golaszewski <[email protected]>

---
 .../devicetree/bindings/gpio/fairchild,74hc595.yaml    | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Documentation/devicetree/bindings/gpio/fairchild,74hc595.yaml +0 -0

index a209c5b4f6e0..da462dddb140 100644

From: Bartosz Golaszewski <[email protected]>

There were other suggested solutions (for instance: just use the existing compatible for the On Semi variant) but I figured the most common approach is to use a fallback value for 100% compatible models and this is what Rob suggested as well.

This reverts the driver change and makes the "onnn,74hc595a" compatible use "fairchild,74hc595" as fallback.

Bartosz Golaszewski (2):
Revert "gpio: 74x164: Add On Semi MC74HC595A compat"
dt-bindings: gpio: fairchild,74hc595: use a fallback for Semi

     MC74HC595A

  .../devicetree/bindings/gpio/fairchild,74hc595.yaml    | 10 ++++++----
  drivers/gpio/gpio-74x164.c                             |  2 --
  2 files changed, 6 insertions(+), 6 deletions(-)

Hi,

Quoted 7 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

There were other suggested solutions (for instance: just use the existing compatible for the On Semi variant) but I figured the most common approach is to use a fallback value for 100% compatible models and this is what Rob suggested as well.

Quoted 2 lines

This reverts the driver change and makes the "onnn,74hc595a" compatible use "fairchild,74hc595" as fallback.

Is there any reason to introduce a new compatible name at all? Does some pre-existing, widely-used DT blob use it in the wild already? If not, then I don't think it's necessary; for any new boards, their DT's authors should just use the pre-existing names.

I'm especially against introducing a new, vendor-specific (On Semi, in this case) name; if we really want to introduce a new compatible, at least make it as generic as possible, i.e. generic,74x595, or even generic,spi-shift-register-output.

Quoted 8 lines

Bartosz Golaszewski (2):
Revert "gpio: 74x164: Add On Semi MC74HC595A compat"
dt-bindings: gpio: fairchild,74hc595: use a fallback for Semi

     MC74HC595A

  .../devicetree/bindings/gpio/fairchild,74hc595.yaml    | 10 ++++++----
  drivers/gpio/gpio-74x164.c                             |  2 --
  2 files changed, 6 insertions(+), 6 deletions(-)

Bence

Quoted 8 lines · Csókás Bence

Quoted 7 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

There were other suggested solutions (for instance: just use the existing compatible for the On Semi variant) but I figured the most common approach is to use a fallback value for 100% compatible models and this is what Rob suggested as well.

Quoted 7 lines

Quoted 2 lines

This reverts the driver change and makes the "onnn,74hc595a" compatible use "fairchild,74hc595" as fallback.

Is there any reason to introduce a new compatible name at all? Does some pre-existing, widely-used DT blob use it in the wild already? If not, then I don't think it's necessary; for any new boards, their DT's authors should just use the pre-existing names.

I don't have a strong opinion on this and will defer to DT maintainers but a similar case I'm familiar with is the at24 EEPROM driver where we've got lots of 1:1 compatible chips and we tend to add new compatibles to DT bindings (with fallbacks to associated atmel models) just for the sake of correct HW description in DTS.

Quoted 4 lines

I'm especially against introducing a new, vendor-specific (On Semi, in this case) name; if we really want to introduce a new compatible, at least make it as generic as possible, i.e. generic,74x595, or even generic,spi-shift-register-output.

If anything, that would have to be the fallback that the driver knows. The first string in the compatible property has to have an actual vendor (I think, I'll let DT maintainers correct me).

Hi Bartosz,

Quoted 17 lines · Bartosz Golaszewski

Quoted 8 lines · Csókás Bence

Quoted 7 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

There were other suggested solutions (for instance: just use the existing compatible for the On Semi variant) but I figured the most common approach is to use a fallback value for 100% compatible models and this is what Rob suggested as well.

Quoted 7 lines

Quoted 2 lines

This reverts the driver change and makes the "onnn,74hc595a" compatible use "fairchild,74hc595" as fallback.

Is there any reason to introduce a new compatible name at all? Does some pre-existing, widely-used DT blob use it in the wild already? If not, then I don't think it's necessary; for any new boards, their DT's authors should just use the pre-existing names.

Quoted 5 lines

I don't have a strong opinion on this and will defer to DT maintainers but a similar case I'm familiar with is the at24 EEPROM driver where we've got lots of 1:1 compatible chips and we tend to add new compatibles to DT bindings (with fallbacks to associated atmel models) just for the sake of correct HW description in DTS.

At24 EEPROMs differ from '595 shift registers in that they provide an API with multiple commands, and some commands or parameter bits may differ among different implementations (but usually these differences are called quirks).

All '595 (I'm deliberately writing it like that) shift registers should be 100% compatible, modulo some electrical specifications (voltage levels, maximum speed, power consumption, ...).

Interestingly, the driver is called gpio-74x164.c, while no '164 compatible value is present. Most important difference is that the '164 lacks the output latch, which is used as chip-select with SPI[1].

Quoted 5 lines

Quoted 4 lines

I'm especially against introducing a new, vendor-specific (On Semi, in this case) name; if we really want to introduce a new compatible, at least make it as generic as possible, i.e. generic,74x595, or even generic,spi-shift-register-output.

Quoted 3 lines

If anything, that would have to be the fallback that the driver knows. The first string in the compatible property has to have an actual vendor (I think, I'll let DT maintainers correct me).

For the inverse operation (parallel in, serial out), there's just "pisosr-gpio".

Quoted 22 lines

At24 EEPROMs differ from '595 shift registers in that they provide an API with multiple commands, and some commands or parameter bits may differ among different implementations (but usually these differences are called quirks).

All '595 (I'm deliberately writing it like that) shift registers should be 100% compatible, modulo some electrical specifications (voltage levels, maximum speed, power consumption, ...).

Interestingly, the driver is called gpio-74x164.c, while no '164 compatible value is present. Most important difference is that the '164 lacks the output latch, which is used as chip-select with SPI[1].

Quoted 8 lines

Quoted 4 lines

I'm especially against introducing a new, vendor-specific (On Semi, in this case) name; if we really want to introduce a new compatible, at least make it as generic as possible, i.e. generic,74x595, or even generic,spi-shift-register-output.

If anything, that would have to be the fallback that the driver knows. The first string in the compatible property has to have an actual vendor (I think, I'll let DT maintainers correct me).

Quoted 3 lines

For the inverse operation (parallel in, serial out), there's just "pisosr-gpio".

Ok, I admit I don't know the correct next step. I'll wait for Krzysztof, Rob or Conor to chime in (on the subject of representing reality - the actual manufacturer - in DTS) and then possibly just remove patches 1-2 from my tree.

Quoted 22 lines · Bartosz Golaszewski

Quoted 22 lines

At24 EEPROMs differ from '595 shift registers in that they provide an API with multiple commands, and some commands or parameter bits may differ among different implementations (but usually these differences are called quirks).

All '595 (I'm deliberately writing it like that) shift registers should be 100% compatible, modulo some electrical specifications (voltage levels, maximum speed, power consumption, ...).

Interestingly, the driver is called gpio-74x164.c, while no '164 compatible value is present. Most important difference is that the '164 lacks the output latch, which is used as chip-select with SPI[1].

Quoted 8 lines

Quoted 4 lines

I'm especially against introducing a new, vendor-specific (On Semi, in this case) name; if we really want to introduce a new compatible, at least make it as generic as possible, i.e. generic,74x595, or even generic,spi-shift-register-output.

If anything, that would have to be the fallback that the driver knows. The first string in the compatible property has to have an actual vendor (I think, I'll let DT maintainers correct me).

Quoted 7 lines

Quoted 2 lines

For the inverse operation (parallel in, serial out), there's just "pisosr-gpio".

Ok, I admit I don't know the correct next step. I'll wait for Krzysztof, Rob or Conor to chime in (on the subject of representing reality - the actual manufacturer - in DTS) and then possibly just remove patches 1-2 from my tree.

Well, folks, I don't know the exact device, so maybe there is no point in a new compatible if there is a claim all devices have same interface and documenting all of them would result in 1000 redundant compatibles... but OTOH, that's what we still do with jedec,spi and at24, so if we can add specific compatibles for these, we can do same also here.

Hi Krzysztof,

Quoted 31 lines · Krzysztof Kozlowski

Quoted 22 lines · Bartosz Golaszewski

Quoted 22 lines

At24 EEPROMs differ from '595 shift registers in that they provide an API with multiple commands, and some commands or parameter bits may differ among different implementations (but usually these differences are called quirks).

All '595 (I'm deliberately writing it like that) shift registers should be 100% compatible, modulo some electrical specifications (voltage levels, maximum speed, power consumption, ...).

Interestingly, the driver is called gpio-74x164.c, while no '164 compatible value is present. Most important difference is that the '164 lacks the output latch, which is used as chip-select with SPI[1].

Quoted 8 lines

Quoted 4 lines

I'm especially against introducing a new, vendor-specific (On Semi, in this case) name; if we really want to introduce a new compatible, at least make it as generic as possible, i.e. generic,74x595, or even generic,spi-shift-register-output.

If anything, that would have to be the fallback that the driver knows. The first string in the compatible property has to have an actual vendor (I think, I'll let DT maintainers correct me).

Quoted 7 lines

Quoted 2 lines

For the inverse operation (parallel in, serial out), there's just "pisosr-gpio".

Ok, I admit I don't know the correct next step. I'll wait for Krzysztof, Rob or Conor to chime in (on the subject of representing reality - the actual manufacturer - in DTS) and then possibly just remove patches 1-2 from my tree.

Quoted 6 lines

Well, folks, I don't know the exact device, so maybe there is no point in a new compatible if there is a claim all devices have same interface and documenting all of them would result in 1000 redundant compatibles... but OTOH, that's what we still do with jedec,spi and at24, so if we can add specific compatibles for these, we can do same also here.

Except that we don't for jedec,spi, unfortunately[1].

At24 and jedec,spi use a complex programming API, with lots of room for deviation and extension. '595 is a pure hardware part[2]: it is just a shift register (driven by SPI clock and MOSI) with a latch (driven by deasserting SPI chip select), without room for deviation. Anything that behaves differently is not a jelly-bean '595 part.

[1] "[PATCH] dt-bindings: mtd: jedec,spi-nor: Document support for more MT25QU parts'

    https://lore.kernel.org/all/363186079b4269891073f620e3e2353cf7d2559a.1669988238.git.geert+renesas@glider.be

[2] Ignoring the rumor that all Microchip I/O expanders are actually pre-programmed PIC microcontrollers ;-)

Hi,

Quoted 7 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

There were other suggested solutions (for instance: just use the existing compatible for the On Semi variant) but I figured the most common approach is to use a fallback value for 100% compatible models and this is what Rob suggested as well.

Quoted 2 lines

This reverts the driver change and makes the "onnn,74hc595a" compatible use "fairchild,74hc595" as fallback.

Is there any reason to introduce a new compatible name at all? Does some