Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [RFC] dmaengine: Add metadata_ops for dma_async_tx_descriptor
To:     Radhey Shyam Pandey <radheys@xilinx.com>,
        "dan.j.williams@intel.com" <dan.j.williams@intel.com>,
        "vkoul@kernel.org" <vkoul@kernel.org>
CC:     "dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "lars@metafoo.de" <lars@metafoo.de>
References: <20180815105704.26498-1-peter.ujfalusi@ti.com>
 <CY4PR0201MB36192D111C6EE8AC4E86C173C73E0@CY4PR0201MB3619.namprd02.prod.outlook.com>
From:   Peter Ujfalusi <peter.ujfalusi@ti.com>
Message-ID: <38aa48ba-5cf9-da12-bef8-b75e22f8b822@ti.com>
Date:   Fri, 17 Aug 2018 09:30:30 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.9.0
MIME-Version: 1.0
In-Reply-To: <CY4PR0201MB36192D111C6EE8AC4E86C173C73E0@CY4PR0201MB3619.namprd02.prod.outlook.com>
Content-Type: text/plain; charset="utf-8"
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Radhey,

On 2018-08-16 16:29, Radhey Shyam Pandey wrote:
>> +/**
>> + * enum dma_desc_metadata_mode - per descriptor metadata mode types
>> supported
>> + * @DESC_METADATA_CLIENT - the metadata buffer is allocated/provided by
>> the
>> + *  client driver and it is attached (via the dmaengine_desc_attach_metadata()
>> + *  helper) to the descriptor.
>> + * @DESC_METADATA_EMBEDDED - the metadata buffer is
>> allocated/managed by the DMA
> Just a thought - We can rename it to DESC_METADATA_ENGINE? 
> i.e metadata allocation place - >  dma client/engine.

Sounds good.

> 
>> + *  driver. The client driver can ask for the pointer, maximum size and the
>> + *  currently used size of the metadata and can directly updata or read it.
> /s/updata/update
> 
>> + *  dmaengine_desc_get_metadata_ptr() and
>> dmaengine_desc_set_metadata_len() is
>> + *  provided as helper functions.
> It will be helpful if we add description for both DESC_METADATA_EMBEDDED 
> modes i.e DMA_DEV_TO_MEM and MEM_TO_DEV types. I think in DEV_TO_MEM
> we don't need to set_metadata_len(). Length will provided by DMA engine.

I agree, it is better to extend the explanation on the two modes.

...

>> +static inline int _desc_check_and_set_metadata_mode(
>> +	struct dma_async_tx_descriptor *desc, enum
>> dma_desc_metadata_mode mode)
>> +{
>> +	/* Make sure that the metadata mode is not mixed */
>> +	if (!desc->desc_metadata_mode) {
> Minor nit - we can refactor this code to have failure path early.

I don't think it would help readability, to move the failure case first:

if (desc->desc_metadata_mode &&
    (desc->desc_metadata_mode != mode)) {
	return -EINVAL;
} else if (!desc->desc_metadata_mode) {
	if (dmaengine_is_metadata_mode_supported(desc->chan, mode))
			desc->desc_metadata_mode = mode;
		else
			return -ENOTSUPP;
}

return 0;

> 
>> +		if (dmaengine_is_metadata_mode_supported(desc->chan,
>> mode))
>> +			desc->desc_metadata_mode = mode;
>> +		else
>> +			return -ENOTSUPP;
>> +	} else if (desc->desc_metadata_mode != mode) {
>> +		return -EINVAL;
>> +	}
>> +
>> +	return 0;
>> +}

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki