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Message-Id: <20231012.154444.1868411153601666717.fujita.tomonori@gmail.com> Date: Thu, 12 Oct 2023 15:44:44 +0900 (JST) From: FUJITA Tomonori <fujita.tomonori@...il.com> To: boqun.feng@...il.com Cc: fujita.tomonori@...il.com, netdev@...r.kernel.org, rust-for-linux@...r.kernel.org, andrew@...n.ch, miguel.ojeda.sandonis@...il.com, greg@...ah.com, tmgross@...ch.edu Subject: Re: [PATCH net-next v3 1/3] rust: core abstractions for network PHY drivers On Wed, 11 Oct 2023 23:34:18 -0700 Boqun Feng <boqun.feng@...il.com> wrote: > On Thu, Oct 12, 2023 at 02:58:24PM +0900, FUJITA Tomonori wrote: >> On Wed, 11 Oct 2023 11:29:45 -0700 >> Boqun Feng <boqun.feng@...il.com> wrote: >> >> > On Mon, Oct 09, 2023 at 10:39:10AM +0900, FUJITA Tomonori wrote: >> > [...] >> >> +impl Device { >> >> + /// Creates a new [`Device`] instance from a raw pointer. >> >> + /// >> >> + /// # Safety >> >> + /// >> >> + /// For the duration of the lifetime 'a, the pointer must be valid for writing and nobody else >> >> + /// may read or write to the `phy_device` object. >> >> + pub unsafe fn from_raw<'a>(ptr: *mut bindings::phy_device) -> &'a mut Self { >> >> + unsafe { &mut *ptr.cast() } >> >> + } >> >> + >> >> + /// Gets the id of the PHY. >> >> + pub fn phy_id(&mut self) -> u32 { >> > >> > This function doesn't modify the `self`, why does this need to be a >> > `&mut self` function? Ditto for a few functions in this impl block. >> > >> > It seems you used `&mut self` for all the functions, which looks like >> > more design work is required here. >> >> Ah, I can drop all the mut here. > > It may not be that easy... IIUC, most of the functions in the `impl` > block can only be called correctly with phydev->lock held. In other > words, their usage requires exclusive accesses. We should somehow > express this in the type system, otherwise someone may lose track on > this requirement in the future (for example, calling any function > without the lock held). > > A simple type trick comes to me is that > > impl Device { > // rename `from_raw` into `assume_locked` > pub unsafe fn assume_locked<'a>(ptr: *mut bindings::phy_device) -> &'a LockedDevice { > ... > } > } Hmm, the concept of PHYLIB is that a driver never play with a lock. From the perspective of PHYLIB, this abstraction is a PHY driver. The abstraction should not touch the lock. How can someone lose track on this requirement? The abstraction creates a Device instance only inside the callbacks.
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