linux-kernel - Re: [PATCH] i3c: master: svc: fix signed/unsigned mismatch in dynamic address assignment

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Message-ID: <Z9mGK0x8fsWvbTvo@qasdev.system>
Date: Tue, 18 Mar 2025 14:41:47 +0000
From: Qasim Ijaz <qasdev00@...il.com>
To: Frank Li <Frank.li@....com>
Cc: miquel.raynal@...tlin.com, alexandre.belloni@...tlin.com,
	linux-i3c@...ts.infradead.org, imx@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i3c: master: svc: fix signed/unsigned mismatch in
 dynamic address assignment

On Tue, Mar 18, 2025 at 09:40:17AM -0400, Frank Li wrote:
> On Mon, Mar 17, 2025 at 10:15:16AM +0000, Qasim Ijaz wrote:
> > svc_i3c_master_do_daa_locked() declares dyn_addr as an unsigned int
> > however it initialises it with i3c_master_get_free_addr() which
> > returns a signed int type and then attempts to check if dyn_addr is
> > less than 0. Unsigned integers cannot be less than 0, so the check
> > is essentially redundant. Furthermore i3c_master_get_free_addr()
> > could return -ENOMEM which an unsigned int cannot store.
> >
> > Fix this by capturing the return value of i3c_master_get_free_addr()
> > in a signed int ‘dyn_addr_ret’. If that value is negative, return
> > an error. Otherwise, assign it to the unsigned int ‘dyn_addr’ once
> > we know it’s valid.
> >
> > Fixes: 4008a74e0f9b ("i3c: master: svc: Fix npcm845 FIFO empty issue")
> > Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
> > ---
> 
> Thank you for your patch, but similar one was already applied
> https://lore.kernel.org/linux-i3c/174225158210.1593610.10018812780731849409.b4-ty@bootlin.com/T/#m5120e1c362e7e57f4cab139a45410fde421c2f37
>

Hi Frank 
 
I sent a fix for this issue on the 9th March, which is before the patch
you linked which was sent on the 10th March.

You can view my orignal patch here:

https://lore.kernel.org/all/20250309164314.15039-1-qasdev00@gmail.com/

Thanks
Qasim
> Frank
> >  drivers/i3c/master/svc-i3c-master.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> > index f22fb9e75142..eea08f00d7ce 100644
> > --- a/drivers/i3c/master/svc-i3c-master.c
> > +++ b/drivers/i3c/master/svc-i3c-master.c
> > @@ -998,9 +998,10 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
> >  			 * filling within a few hundred nanoseconds, which is significantly
> >  			 * faster compared to the 64 SCL clock cycles.
> >  			 */
> > -			dyn_addr = i3c_master_get_free_addr(&master->base, last_addr + 1);
> > -			if (dyn_addr < 0)
> > +			int dyn_addr_ret = i3c_master_get_free_addr(&master->base, last_addr + 1);
> > +			if (dyn_addr_ret < 0)
> >  				return -ENOSPC;
> > +			dyn_addr = dyn_addr_ret;
> >
> >  			writel(dyn_addr, master->regs + SVC_I3C_MWDATAB);
> >
> > --
> > 2.39.5
> >