Messages in this thread |  | | Date | Wed, 21 May 2025 20:36:10 +0200 | | Subject | Re: [PATCH v5 4/9] rust: device: Enable printing fwnode name and path | | From | "Remo Senekowitsch" <> |
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On Wed May 21, 2025 at 6:58 PM CEST, Greg Kroah-Hartman wrote: > On Wed, May 21, 2025 at 03:03:07PM +0200, Remo Senekowitsch wrote: >> On Wed May 21, 2025 at 2:02 PM CEST, Greg Kroah-Hartman wrote: >> > On Tue, May 20, 2025 at 10:00:19PM +0200, Remo Senekowitsch wrote: >> >> Add two new public methods `display_name` and `display_path` to >> >> `FwNode`. They can be used by driver authors for logging purposes. In >> >> addition, they will be used by core property abstractions for automatic >> >> logging, for example when a driver attempts to read a required but >> >> missing property. >> >> >> >> Signed-off-by: Remo Senekowitsch <remo@buenzli.dev> >> >> --- >> >> rust/kernel/device/property.rs | 72 ++++++++++++++++++++++++++++++++++ >> >> 1 file changed, 72 insertions(+) >> >> >> >> diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs >> >> index 70593343bd811..6ccc7947f9c31 100644 >> >> --- a/rust/kernel/device/property.rs >> >> +++ b/rust/kernel/device/property.rs >> >> @@ -32,6 +32,78 @@ pub(crate) fn as_raw(&self) -> *mut bindings::fwnode_handle { >> >> self.0.get() >> >> } >> >> >> >> + /// Returns an object that implements [`Display`](core::fmt::Display) for >> >> + /// printing the name of a node. >> >> + pub fn display_name(&self) -> impl core::fmt::Display + '_ { >> >> + struct FwNodeDisplayName<'a>(&'a FwNode); >> >> + >> >> + impl core::fmt::Display for FwNodeDisplayName<'_> { >> >> + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { >> >> + // SAFETY: self is valid by its type invariant >> >> + let name = unsafe { bindings::fwnode_get_name(self.0.as_raw()) }; >> >> + if name.is_null() { >> >> + return Ok(()); >> > >> > So if there is no name, you are returning Ok()? Are you sure that's ok >> > to do? What will the result of the string look like then? >> >> In that case we're not writing anything to the formatter, which is >> equivalent to an empty string. `Ok(())` means that writing succeeded. >> >> I assumed that a valid node would always have a name. And we're >> guaranteed to have a valid node. So I assumed this case would never >> happen and didn't think too hard about it. But even if a valid node has >> not name, empty string is probably the correct thing, right? > > I don't know what this "name" is used for. An empty string might not be > what you want to use here, given that you could be naming something > based on it, right? fwnode_get_name() is used for many things, > including the detection if a name is not present at all, and if not, > then the code needs to clean up and abort. > > So what exactly are you going to be using this for?
Valid question... I'm not using it for anything. I was trying to match the C API which has capabilities to print a fwnode's name and full path. I think the format specifiers are %pfwP and %pfwf if I'm reading the source correctly. It also looks to me like the C API for printing fwnode names does the same thing - print nothing if the name is null. [1] [2]
[1] https://elixir.bootlin.com/linux/v6.14.7/source/lib/vsprintf.c#L2242 [2] https://elixir.bootlin.com/linux/v6.14.7/source/lib/vsprintf.c#L711
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