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Date: Thu, 23 Sep 2021 12:51:34 +0000 From: Akhil R <akhilrajeev@...dia.com> To: Jonathan Hunter <jonathanh@...dia.com> CC: "dan.j.williams@...el.com" <dan.j.williams@...el.com>, "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>, Krishna Yarlagadda <kyarlagadda@...dia.com>, Laxman Dewangan <ldewangan@...dia.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>, "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>, Rajesh Gumasta <rgumasta@...dia.com>, "thierry.reding@...il.com" <thierry.reding@...il.com>, "vkoul@...nel.org" <vkoul@...nel.org>, Pavan Kunapuli <pkunapuli@...dia.com> Subject: RE: [PATCH v6 2/4] dmaengine: tegra: Add tegra gpcdma driver > On 22/09/2021 15:46, Akhil R wrote: > > > >> On 17/09/2021 15:11, Akhil R wrote: > >>> +static int tegra_dma_slave_config(struct dma_chan *dc, > >>> + struct dma_slave_config *sconfig) { > >>> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc); > >>> + > >>> + if (tdc->dma_desc) { > >>> + dev_err(tdc2dev(tdc), "Configuration not allowed\n"); > >>> + return -EBUSY; > >>> + } > >>> + > >>> + memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig)); > >>> + if (tdc->slave_id == -1) > >>> + tdc->slave_id = sconfig->slave_id; > >>> + > >>> + tdc->config_init = true; > >>> + return 0; > >>> +} > >> > >> So you have a function to reserve a slave ID, but you don't check > >> here if it is already reserved. > > slave-id is reserved considering the direction as well. > > 'direction' is available only during prep_slave_sg function, I guess. > > Sorry I don't understand what you mean by that. I mean, it would not be possible to check if the sid is in use without knowing if the direction is MEM_TO_DEV or DEV_TO_MEM. The bitmask to check the sid reservation is separate for MEM_TO_DEV and DEV_TO_MEM. To get the direction parameter, we would need to wait till dma_prep_slave_sg is called, I guess. I saw in the documentation that the 'direction' element in dma_slave_config struct is deprecated and should use the value passed to dma_prep_slave_sg(). Regards, Akhil -- nvpublic
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