linux-kernel - Re: [RFC] dmaengine: Add metadat_ops for dma_async_tx

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Message-ID: <20180710055230.GB3219@vkoul-mobl>
Date:   Tue, 10 Jul 2018 11:22:30 +0530
From:   Vinod <vkoul@...nel.org>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     radheys@...inx.com, vinod.koul@...el.com, lars@...afoo.de,
        michal.simek@...inx.com, linux-kernel@...r.kernel.org,
        dmaengine@...r.kernel.org, dan.j.williams@...el.com,
        appanad@...inx.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC] dmaengine: Add metadat_ops for dma_async_tx_descriptor


Hey Peter,

Sorry for late response on this..

On 01-06-18, 13:24, Peter Ujfalusi wrote:
> If the DMA supports per descriptor metadata it can implement the attach,
> get_ptr/set_len callbacks.
> 
> Client drivers must only use either attach or get_ptr/set_len to avoid
> miss configuration.
> 
> Wrappers are also added for the metadata_ops:
> dmaengine_desc_attach_metadata()
> dmaengine_desc_get_metadata_ptr()
> dmaengine_desc_set_metadata_len()
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> ---
> Hi,
> 
> since attachments are bouncing back, I send the patch separately
> 
> Regards,
> Peter
> 
>  include/linux/dmaengine.h | 50 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 50 insertions(+)
> 
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 51fbb861e84b..ac42ace36aa3 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -491,6 +491,18 @@ struct dmaengine_unmap_data {
>  	dma_addr_t addr[0];
>  };
>  
> +struct dma_async_tx_descriptor;
> +
> +struct dma_descriptor_metadata_ops {
> +	int (*attach)(struct dma_async_tx_descriptor *desc, void *data,
> +		      size_t len);

How does one detach? When should the client free up the memory, IOW when
does dma driver drop ref to data.

> +
> +	void *(*get_ptr)(struct dma_async_tx_descriptor *desc,
> +			 size_t *payload_len, size_t *max_len);

so what is this supposed to do..?

> +	int (*set_len)(struct dma_async_tx_descriptor *desc,
> +		       size_t payload_len);

attach already has length, so how does this help?

> +};
> +
>  /**
>   * struct dma_async_tx_descriptor - async transaction descriptor
>   * ---dma generic offload fields---
> @@ -520,6 +532,7 @@ struct dma_async_tx_descriptor {
>  	dma_async_tx_callback_result callback_result;
>  	void *callback_param;
>  	struct dmaengine_unmap_data *unmap;
> +	struct dma_descriptor_metadata_ops *metadata_ops;
>  #ifdef CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH
>  	struct dma_async_tx_descriptor *next;
>  	struct dma_async_tx_descriptor *parent;
> @@ -932,6 +945,43 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_memcpy(
>  						    len, flags);
>  }
>  
> +static inline int dmaengine_desc_attach_metadata(
> +		struct dma_async_tx_descriptor *desc, void *data, size_t len)
> +{
> +	if (!desc)
> +		return 0;
> +
> +	if (!desc->metadata_ops || !desc->metadata_ops->attach)
> +		return -ENOTSUPP;
> +
> +	return desc->metadata_ops->attach(desc, data, len);
> +}
> +
> +static inline void *dmaengine_desc_get_metadata_ptr(
> +		struct dma_async_tx_descriptor *desc, size_t *payload_len,
> +		size_t *max_len)
> +{
> +	if (!desc)
> +		return NULL;
> +
> +	if (!desc->metadata_ops || !desc->metadata_ops->get_ptr)
> +		return ERR_PTR(-ENOTSUPP);
> +
> +	return desc->metadata_ops->get_ptr(desc, payload_len, max_len);
> +}
> +
> +static inline int dmaengine_desc_set_metadata_len(
> +		struct dma_async_tx_descriptor *desc, size_t payload_len)
> +{
> +	if (!desc)
> +		return 0;
> +
> +	if (!desc->metadata_ops || !desc->metadata_ops->set_len)
> +		return -ENOTSUPP;
> +
> +	return desc->metadata_ops->set_len(desc, payload_len);
> +}
> +
>  /**
>   * dmaengine_terminate_all() - Terminate all active DMA transfers
>   * @chan: The channel for which to terminate the transfers
> -- 
> Peter
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> 
> --
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-- 
~Vinod