linux-kernel - Re: [PATCH V2 07/15] coresight: tmc: allocating memory when needed

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Date:	Tue, 19 Apr 2016 14:14:59 +0100
From:	Suzuki K Poulose <Suzuki.Poulose@....com>
To:	Mathieu Poirier <mathieu.poirier@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 07/15] coresight: tmc: allocating memory when needed

On 19/04/16 13:55, Suzuki K Poulose wrote:
> On 12/04/16 18:54, Mathieu Poirier wrote:
>> In it's current form the TMC probe() function allocates
>> trace buffer memory at boot time, event if coresight isn't
>> used.  This is highly inefficient since trace buffers can
>> occupy a lot of memory that could be used otherwised.
>>
>> This patch allocates trace buffers on the fly, when the
>> coresight subsystem is solicited.  Allocated buffers are
>> released when traces are read using the device descriptors
>> under /dev.
>>

>>       /* Wait for TMCSReady bit to be set */
>> @@ -110,19 +108,68 @@ static void tmc_etf_disable_hw(struct tmc_drvdata *drvdata)
>>
>>   static int tmc_enable_etf_sink(struct coresight_device *csdev, u32 mode)
>>   {
>> +    bool allocated = false;
>
> nit: does "used" or buf_used sound more suitable than allocated ?
>
>> +    char *buf = NULL;
>>       unsigned long flags;
>>       struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>>
>> +     /* This shouldn't be happening */
>> +    WARN_ON(mode != CS_MODE_SYSFS);

And we should proceed no further. Return immediately.