On Fri 14 Feb 2025 at 17:33, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Feb 11, 2025 at 06:27:58PM +0100, Jerome Brunet wrote: >> Add helper functions to create a device on the auxiliary bus. >> >> This is meant for fairly simple usage of the auxiliary bus, to avoid having >> the same code repeated in the different drivers. >> >> Suggested-by: Stephen Boyd <sboyd@xxxxxxxxxx> >> Cc: Arnd Bergmann <arnd@xxxxxxxx> >> Signed-off-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx> >> --- >> drivers/base/auxiliary.c | 88 +++++++++++++++++++++++++++++++++++++++++++ >> include/linux/auxiliary_bus.h | 10 +++++ >> 2 files changed, 98 insertions(+) > > I like the idea, see much the same of what I recently did for the "faux" > bus here: > https://lore.kernel.org/all/2025021023-sandstorm-precise-9f5d@gregkh/ Reading this, I'm getting the feeling that some (most?) simple auxiliary driver might be better off migrating to "faux", instead of what I'm proposing here ? Is this what you are suggesting ? Few Q: Is there some sort of 'platform_data' (sorry for the lack of a better term, no provocation intended ;) ) ... it there a simple way to pass an arbitrary struct to the created device with 'faux' ? The difference between aux and faux I'm seeing it that aux seems to decouple things a bit more. The only thing aux needs is a module name to pop something up, while faux needs a reference to the ops instead. I can see the appeal to use aux for maintainers trying to decouple different subsystems. > > Some review comments: > >> diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c >> index afa4df4c5a3f371b91d8dd8c4325495d32ad1291..0f697c9c243dc9a50498a52362806db594345faf 100644 >> --- a/drivers/base/auxiliary.c >> +++ b/drivers/base/auxiliary.c >> @@ -385,6 +385,94 @@ void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv) >> } >> EXPORT_SYMBOL_GPL(auxiliary_driver_unregister); >> >> +static void auxiliary_device_release(struct device *dev) >> +{ >> + struct auxiliary_device *auxdev = to_auxiliary_dev(dev); >> + >> + kfree(auxdev); >> +} >> + >> +static struct auxiliary_device *auxiliary_device_create(struct device *dev, >> + const char *modname, >> + const char *devname, >> + void *platform_data, > > Can you have the caller set the platform_data if they need/want it after > the device is created? Or do you need that in the probe callback? My assumption was that it is needed in probe, but I guess that entirely depends on the driver. If that was ever needed, it could be added later I think. > > And can't this be a global function too for those that don't want to > deal with devm stuff? There was a note about that in the cover-letter of the v1 but I did not repeat it after. It can be exported but I had no use for it so I thought It was better not export it until it was actually needed. I really do not have a strong preference over this. > >> + int id) >> +{ >> + struct auxiliary_device *auxdev; >> + int ret; >> + >> + auxdev = kzalloc(sizeof(*auxdev), GFP_KERNEL); >> + if (!auxdev) >> + return ERR_PTR(-ENOMEM); > > Ick, who cares what the error value really is? Why not just do NULL or > a valid pointer? That makes the caller much simpler to handle, right? > Sure why not >> + >> + auxdev->id = id; >> + auxdev->name = devname; >> + auxdev->dev.parent = dev; >> + auxdev->dev.platform_data = platform_data; >> + auxdev->dev.release = auxiliary_device_release; >> + device_set_of_node_from_dev(&auxdev->dev, dev); >> + >> + ret = auxiliary_device_init(auxdev); > > Only way this will fail is if you forgot to set parent or a valid name. > So why not check for devname being non-NULL above this? If auxiliary_device_init() ever changes it would be easy to forget to update that and lead to something nasty to debug, don't you think ? If you are OK with this, I could update in this direction. > >> + if (ret) { >> + kfree(auxdev); >> + return ERR_PTR(ret); >> + } >> + >> + ret = __auxiliary_device_add(auxdev, modname); >> + if (ret) { >> + /* >> + * NOTE: It may look odd but auxdev should not be freed >> + * here. auxiliary_device_uninit() calls device_put() >> + * which call the device release function, freeing auxdev. >> + */ >> + auxiliary_device_uninit(auxdev); > > Yes it is odd, are you SURE you should be calling device_del() on the > device if this fails? auxiliary_device_uninit(), makes sense so why not > just call that here? I'm confused ... I am call auxiliary_device_uninit() here. What do you mean ? > >> + return ERR_PTR(ret); >> + } >> + >> + return auxdev; >> +} >> + >> +static void auxiliary_device_destroy(void *_auxdev) >> +{ >> + struct auxiliary_device *auxdev = _auxdev; >> + >> + auxiliary_device_delete(auxdev); >> + auxiliary_device_uninit(auxdev); >> +} >> + >> +/** >> + * __devm_auxiliary_device_create - create a device on the auxiliary bus >> + * @dev: parent device >> + * @modname: module name used to create the auxiliary driver name. >> + * @devname: auxiliary bus device name >> + * @platform_data: auxiliary bus device platform data >> + * @id: auxiliary bus device id >> + * >> + * Device managed helper to create an auxiliary bus device. >> + * The device create matches driver 'modname.devname' on the auxiliary bus. >> + */ >> +struct auxiliary_device *__devm_auxiliary_device_create(struct device *dev, >> + const char *modname, >> + const char *devname, >> + void *platform_data, >> + int id) >> +{ >> + struct auxiliary_device *auxdev; >> + int ret; >> + >> + auxdev = auxiliary_device_create(dev, modname, devname, platform_data, id); >> + if (IS_ERR(auxdev)) >> + return auxdev; >> + >> + ret = devm_add_action_or_reset(dev, auxiliary_device_destroy, >> + auxdev); > > Oh this is going to be messy, but I trust that callers know what they > are doing here. Good luck! :) > > thanks, > > greg k-h -- Jerome
