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Message-ID: <20241021120254.76831170@xps-13>
Date: Mon, 21 Oct 2024 12:02:54 +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 Tue, 08 Oct 2024 11:18:25 -0400:
> 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>
Reviewed-by: Miquel Raynal <miquel.raynal@...tlin.com>
Thanks,
Miquèl
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