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Message-ID: <c9348be9-7b9e-ebf8-b787-e6b3e0724b4a@kernel.org>
Date:   Sat, 22 Apr 2023 07:07:41 +0900
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Subject: Re: [PATCH] drivers/ata: Improve performance and readability
To:     Yahu Gao <yahu.gao@outlook.com>
Cc:     linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org,
        Yahu Gao <gaoyh12@lenovo.com>, Jiwei Sun <sunjw10@lenovo.com>
References: <OS3P286MB06322266ED2913AF0F6172219E609@OS3P286MB0632.JPNP286.PROD.OUTLOOK.COM>
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From:   Damien Le Moal <dlemoal@kernel.org>
Organization: Western Digital Research
In-Reply-To: <OS3P286MB06322266ED2913AF0F6172219E609@OS3P286MB0632.JPNP286.PROD.OUTLOOK.COM>
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On 4/21/23 21:54, Yahu Gao wrote:
> From: Yahu Gao <gaoyh12@lenovo.com>
> 

The patch title should start with:

ata: libata-core: ...

And let's be honest here: this is not the hot path and you are optimizing a
single "if" condition for a series of commands that will take 10s of ms to
execute. So this is *not* about performance. So update the patch title please.

> Replace conditions of avoid issuing [P]IDENTIFY to PMP.
> 
> Reviewed-by: Jiwei Sun <sunjw10@lenovo.com>
> Signed-off-by: Yahu Gao <gaoyh12@lenovo.com>
> 
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index 14c17c3bda4e..53f65d751189 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -3802,11 +3802,7 @@ int ata_dev_revalidate(struct ata_device *dev, unsigned int new_class,
>  		return -ENODEV;
>  
>  	/* fail early if !ATA && !ATAPI to avoid issuing [P]IDENTIFY to PMP */
> -	if (ata_class_enabled(new_class) &&
> -	    new_class != ATA_DEV_ATA &&
> -	    new_class != ATA_DEV_ATAPI &&
> -	    new_class != ATA_DEV_ZAC &&
> -	    new_class != ATA_DEV_SEMB) {
> +	if (new_class == ATA_DEV_PMP) {

Using a switch-case here may actually make things even more readable.

>  		ata_dev_info(dev, "class mismatch %u != %u\n",
>  			     dev->class, new_class);
>  		rc = -ENODEV;