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Date: Thu, 14 May 2015 22:31:39 +0200 From: Robert Jarzmik <robert.jarzmik@...e.fr> To: Maxime Ripard <maxime.ripard@...e-electrons.com> Cc: Vinod Koul <vinod.koul@...el.com>, Jonathan Corbet <corbet@....net>, Daniel Mack <daniel@...que.org>, Haojian Zhuang <haojian.zhuang@...il.com>, dmaengine@...r.kernel.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCH v3 6/6] Documentation: dmaengine: document DMA_CTRL_ACK Maxime Ripard <maxime.ripard@...e-electrons.com> writes: > Hi Robert, > >> * DMA_CTRL_ACK >> - - Undocumented feature >> - - No one really has an idea of what it's about, besides being >> - related to reusing the DMA transaction descriptors or having >> - additional transactions added to it in the async-tx API >> - - Useless in the case of the slave API >> + - if set, the TX transfer can be reused after being completed. > > Your sentences should start with an upper-case letter. Ack. >> + - there is a guarantee the TX won't be freed until it is acked >> + by async_tx_ack() > > We never talked about what a "TX transfer" is in the > documentation. That should be documented. I'll remove the "TX", the transfer is widely used in this documentation. > >> + - as a consequence, if a device driver wants to skip the dma_map_sg() and >> + dma_unmap_sg() because the DMA'd data wasn't used, it can resubmit the >> + transfer right after its completion. > > From a provider PoV, the data should always be mapped and / or > allocated in coherent way, so I'm not sure how does that's relevant in > the provider doc. It's relevant because it says the mapping/unmapping is not necessary _between_ 2 submission of a transfer. This implies it is mapped, as it is a requirement for the very first submission. > Also, we should still mention that it's !slave API only. Certainly not, it's fully slave API, that's the purpose of this patch. -- Robert -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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