linux-kernel - Re: [PATCH v7 2/3] i3c: master: Extend address status bit to 4 and add I3C_ADDR_SLOT_EXT

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Message-ID: <20241017094059.4e4ed56d@xps-13>
Date: Thu, 17 Oct 2024 09:40:59 +0200
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Frank Li <Frank.li@....com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
 linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org, arnd@...db.de,
 bbrezillon@...nel.org, boris.brezillon@...labora.com,
 conor.culhane@...vaco.com, gregkh@...uxfoundation.org, imx@...ts.linux.dev,
 pthombar@...ence.com, ravindra.yashvant.shinde@....com
Subject: Re: [PATCH v7 2/3] i3c: master: Extend address status bit to 4 and
 add I3C_ADDR_SLOT_EXT_DESIRED

Hi Frank,

Frank.li@....com wrote on Wed, 16 Oct 2024 12:09:03 -0400:

> On Tue, Oct 08, 2024 at 11:18:25AM -0400, Frank Li wrote:
> > Extend the address status bit to 4 and introduce the
> > I3C_ADDR_SLOT_EXT_DESIRED macro to indicate that a device prefers a
> > specific address. This is generally set by the 'assigned-address' in the
> > device tree source (dts) file.
> >
> >  ┌────┬─────────────┬───┬─────────┬───┐
> >  │S/Sr│ 7'h7E RnW=0 │ACK│ ENTDAA  │ T ├────┐
> >  └────┴─────────────┴───┴─────────┴───┘    │
> >  ┌─────────────────────────────────────────┘
> >  │  ┌──┬─────────────┬───┬─────────────────┬────────────────┬───┬─────────┐
> >  └─►│Sr│7'h7E RnW=1  │ACK│48bit UID BCR DCR│Assign 7bit Addr│PAR│ ACK/NACK│
> >     └──┴─────────────┴───┴─────────────────┴────────────────┴───┴─────────┘
> >
> > Some master controllers (such as HCI) need to prepare the entire above
> > transaction before sending it out to the I3C bus. This means that a 7-bit
> > dynamic address needs to be allocated before knowing the target device's
> > UID information.
> >
> > However, some I3C targets may request specific addresses (called as
> > "init_dyn_addr"), which is typically specified by the DT-'s
> > assigned-address property. Lower addresses having higher IBI priority. If
> > it is available, i3c_bus_get_free_addr() preferably return a free address
> > that is not in the list of desired addresses (called as "init_dyn_addr").
> > This allows the device with the "init_dyn_addr" to switch to its
> > "init_dyn_addr" when it hot-joins the I3C bus. Otherwise, if the
> > "init_dyn_addr" is already in use by another I3C device, the target device
> > will not be able to switch to its desired address.
> >
> > If the previous step fails, fallback returning one of the remaining
> > unassigned address, regardless of its state in the desired list.
> >
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---  
> 
> Miquel:
> 
> 	Do you have a chance to check this patch again?

No worries, it's in my todo list ;)

Thanks,
Miquèl