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From: Thomas Monjalon <thomas@monjalon.net>
To: fengchengwen <fengchengwen@huawei.com>,
	Amit Prakash Shukla <amitprakashs@marvell.com>
Cc: Kevin Laatz <kevin.laatz@intel.com>,
	Bruce Richardson <bruce.richardson@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,  Jerin Jacob <jerinj@marvell.com>,
	Vamsi Krishna Attunuru <vattunuru@marvell.com>,
	Nithin Kumar Dabilpuram <ndabilpuram@marvell.com>,
	Anoob Joseph <anoobj@marvell.com>,
	"mb@smartsharesystems.com" <mb@smartsharesystems.com>
Subject: Re: [EXT] Re: [PATCH v2] lib/dmadev: get DMA device using device ID
Date: Fri, 09 Feb 2024 12:18:25 +0100	[thread overview]
Message-ID: <2153070.3Lj2Plt8kZ@thomas> (raw)
In-Reply-To: <PH0PR18MB516746E466A32A48E4D73D34C84B2@PH0PR18MB5167.namprd18.prod.outlook.com>

09/02/2024 12:05, Amit Prakash Shukla:
> > On 2024/2/9 0:25, Thomas Monjalon wrote:
> > > 19/12/2023 12:00, Amit Prakash Shukla:
> > >> +struct rte_dma_dev *
> > >> +rte_dma_pmd_get_dev_by_id(const int dev_id)
> > > const does not make sense here for an int parameter.
> > 
> > 
> > I think it could be OK with const even if the parameter is not pointer.
> > 
> > However, most DPDK APIs do not have const for simple types (e.g.
> > int/uin16_t).
> > 
> > In this aspect, I think it's also OK to remove const of here for consistency.
> > 
> > 
> > >
> > >> +{
> > >> +	if (!rte_dma_is_valid(dev_id))
> > >> +		return NULL;
> > >> +
> > >> +	return &rte_dma_devices[dev_id];
> > >> +}
> > > [...]
> > >> +/**
> > >> + * @internal
> > >> + * Get the rte_dma_dev structure device pointer for the device id.
> > >> + *
> > >> + * @param dev_id
> > >> + *   Device ID value to select the device structure.
> > > This comment is not explanatory.
> > > What is an ID? Where does it come from?
> > > Where can we see such ID for DMA device?
> > 
> > This new API is used in the event-dma driver of cnxk [1]:
> > 
> > The rte_event_dma_adapter_vchan_add has parameter of dma_dev_id, and it
> > then
> > 
> > invoke (*dev->dev_ops->dma_adapter_vchan_add)(dev, dma_dev_id, vchan,
> > event),
> > 
> > at cnxk driver, this ops will check whether the DMA is
> > cnxk_dmadev_pci_driver.
> > 
> > I think this is because the cnxk's event-and-dma implement has deep coupling
> > 
> > (because the cnxk's event device could interact with another vendor's
> > dma device).
> > 
> > 
> > Maybe we should think of a better way to solve this kind of coupling
> > problem.
> 
> Id, is the DMA dev id which is used in looking up DMA dev. This API is in-line with the other libraries.
> Crypto library has an api rte_cryptodev_pmd_get_dev to get crypto device based on device id.

OK I think I understand.
It is the library ID, the same as returned by
int rte_dma_get_dev_id_by_name(const char *name);

I can remove the const and apply if you are OK.
I would just change this comment:

+ * @param dev_id
+ *   Device ID value to select the device structure.

into

+ *   DMA device index in dmadev library.




  reply	other threads:[~2024-02-09 11:18 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-08  7:55 [PATCH] " Amit Prakash Shukla
2023-12-09  7:11 ` fengchengwen
2023-12-18 10:41   ` [EXT] " Amit Prakash Shukla
2023-12-11 10:23 ` Bruce Richardson
2023-12-18 11:27   ` [EXT] " Amit Prakash Shukla
2023-12-19 11:00 ` [PATCH v2] " Amit Prakash Shukla
2024-01-08 14:47   ` Anoob Joseph
2024-02-06  6:24     ` Amit Prakash Shukla
2024-02-08 16:25   ` Thomas Monjalon
2024-02-09  8:18     ` fengchengwen
2024-02-09 11:05       ` [EXT] " Amit Prakash Shukla
2024-02-09 11:18         ` Thomas Monjalon [this message]
2024-02-09 11:30           ` Amit Prakash Shukla
2024-02-09 17:36             ` Thomas Monjalon

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