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From: Bin Meng <bmeng.cn@gmail.com>
To: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
Cc: Frank Chang <frank.chang@sifive.com>,
	"open list:RISC-V" <qemu-riscv@nongnu.org>,
	Alistair Francis <Alistair.Francis@wdc.com>,
	"qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>,
	Markus Armbruster <armbru@redhat.com>
Subject: Re: [PATCH v2 1/2] hw/dma: sifive_pdma: Fix Control.claim bit detection
Date: Mon, 27 Sep 2021 21:14:32 +0800	[thread overview]
Message-ID: <CAEUhbmU+N65N7NB=AO3O10Y_k0Hu9wnESk6AZ6r2PT4XH+AJAQ@mail.gmail.com> (raw)
In-Reply-To: <3e1507b8-81a4-aa98-5079-e07021be5a73@amsat.org>

Hi Philippe,

On Mon, Sep 27, 2021 at 8:56 PM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> On 9/27/21 09:21, Bin Meng wrote:
> > At present the codes detect whether the DMA channel is claimed by:
> >
> >   claimed = !!s->chan[ch].control & CONTROL_CLAIM;
> >
> > As ! has higher precedence over & (bitwise and), this is essentially
> >
> >   claimed = (!!s->chan[ch].control) & CONTROL_CLAIM;
> >
> > which is wrong, as any non-zero bit set in the control register will
> > produce a result of a claimed channel.
>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>
> Maybe worth adding:
>
> Reported using GCC 9.3.0 on Ubuntu 20.04:
>
>   suggest parentheses around operand of ‘!’ or change ‘&’ to ‘&&’ or ‘!’
> to ‘~’ [-Werror=parentheses]

Actually GCC does not report this as CONTROL_CLAIM happens to be 1 in
this case, as I wrote in the v1 commit message. :)

Regards,
Bin


WARNING: multiple messages have this Message-ID (diff)
From: Bin Meng <bmeng.cn@gmail.com>
To: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
Cc: Alistair Francis <Alistair.Francis@wdc.com>,
	 "qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>,
	"open list:RISC-V" <qemu-riscv@nongnu.org>,
	 Frank Chang <frank.chang@sifive.com>,
	Markus Armbruster <armbru@redhat.com>
Subject: Re: [PATCH v2 1/2] hw/dma: sifive_pdma: Fix Control.claim bit detection
Date: Mon, 27 Sep 2021 21:14:32 +0800	[thread overview]
Message-ID: <CAEUhbmU+N65N7NB=AO3O10Y_k0Hu9wnESk6AZ6r2PT4XH+AJAQ@mail.gmail.com> (raw)
In-Reply-To: <3e1507b8-81a4-aa98-5079-e07021be5a73@amsat.org>

Hi Philippe,

On Mon, Sep 27, 2021 at 8:56 PM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> On 9/27/21 09:21, Bin Meng wrote:
> > At present the codes detect whether the DMA channel is claimed by:
> >
> >   claimed = !!s->chan[ch].control & CONTROL_CLAIM;
> >
> > As ! has higher precedence over & (bitwise and), this is essentially
> >
> >   claimed = (!!s->chan[ch].control) & CONTROL_CLAIM;
> >
> > which is wrong, as any non-zero bit set in the control register will
> > produce a result of a claimed channel.
>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>
> Maybe worth adding:
>
> Reported using GCC 9.3.0 on Ubuntu 20.04:
>
>   suggest parentheses around operand of ‘!’ or change ‘&’ to ‘&&’ or ‘!’
> to ‘~’ [-Werror=parentheses]

Actually GCC does not report this as CONTROL_CLAIM happens to be 1 in
this case, as I wrote in the v1 commit message. :)

Regards,
Bin


  reply	other threads:[~2021-09-27 13:43 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-27  7:21 [PATCH v2 1/2] hw/dma: sifive_pdma: Fix Control.claim bit detection Bin Meng
2021-09-27  7:21 ` [PATCH v2 2/2] hw/dma: sifive_pdma: Don't run DMA when channel is disclaimed Bin Meng
2021-09-28 22:46   ` Alistair Francis
2021-09-28 22:46     ` Alistair Francis
2021-09-28 23:15   ` Alistair Francis
2021-09-28 23:15     ` Alistair Francis
2021-09-27 12:56 ` [PATCH v2 1/2] hw/dma: sifive_pdma: Fix Control.claim bit detection Philippe Mathieu-Daudé
2021-09-27 13:14   ` Bin Meng [this message]
2021-09-27 13:14     ` Bin Meng
2021-09-28 22:45 ` Alistair Francis
2021-09-28 22:45   ` Alistair Francis

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