Re: [Qemu-devel] [Qemu-arm] [PATCH 2/3] hw/sii9022: Add support for Silicon Image SII9022

From: Peter Maydell <peter.maydell@linaro.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: "Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	qemu-arm <qemu-arm@nongnu.org>,
	"QEMU Developers" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [Qemu-arm] [PATCH 2/3] hw/sii9022: Add support for Silicon Image SII9022
Date: Tue, 27 Feb 2018 10:24:31 +0000	[thread overview]
Message-ID: <CAFEAcA_bZ-w7WWUtr8RE6rU8ELLbZpBmeuDnwZ=rLreXgJ6fRg@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdZuNUmZbHnYwUQFJkBNQWADd5tXfc9PYv8amosbO=zn4Q@mail.gmail.com>

On 27 February 2018 at 10:21, Linus Walleij <linus.walleij@linaro.org> wrote:
> On Tue, Feb 27, 2018 at 11:09 AM, Peter Maydell
> <peter.maydell@linaro.org> wrote:
>> On 27 February 2018 at 07:41, Linus Walleij <linus.walleij@linaro.org> wrote:
>>> On Sat, Feb 17, 2018 at 7:32 PM, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>>>
>>>> [Me]
>>>>> +#define DEBUG_SII9022 0
>>>>> +
>>>>> +#define DPRINTF(fmt, ...) \
>>>>> +    do { \
>>>>> +        if (DEBUG_SII9022) { \
>>>>> +            printf("sii9022: " fmt, ## __VA_ARGS__); \
>>>>> +        } \
>>>>> +    } while (0)
>>>>
>>>> Can you replace DPRINTF() by trace events?
>>>
>>> Absolutely but which ones?
>>>
>>> I do not feel senior enough to also invent new trace events
>>> for displays or I2C devices...
>>
>> Just put a trace event where you've put DPRINTF debug statements.
>
> Yeah, hm the question might be silly or something but I don't
> know how to do that.

docs/devel/tracing.txt describes them, but basically:
 * include "trace.h"
 * define trace events with a line for each in the trace-events
   file for the subdirectory (basically a function prototype-ish
   thing followed by a printf-style format string)
 * call them like normal function calls with a trace_ prefix

commit 1b640aa9292bc00beb441e97d862ba322a7ba18d is a recent one
which converted some DRINTFs in hw/sd/sd.c to trace events.

thanks
-- PMM