Messages in this thread | | | Date | Wed, 27 Nov 2013 12:22:11 +0200 | From | "ivan.khoronzhuk" <> | Subject | Re: [PATCH 07/12] memory: davinci-aemif: introduce AEMIF driver |
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On 11/27/2013 02:37 AM, Brian Norris wrote: > On Tue, Nov 26, 2013 at 01:26:44PM -0500, Santosh Shilimkar wrote: >> On Tuesday 26 November 2013 12:21 PM, Sekhar Nori wrote: >>> On 11/26/2013 8:35 PM, Santosh Shilimkar wrote: >>>> On Tuesday 26 November 2013 02:20 AM, Sekhar Nori wrote: >>>>> On Monday 11 November 2013 10:36 PM, Khoronzhuk, Ivan wrote: >>>>>> +static int davinci_aemif_probe(struct platform_device *pdev) >>>>>> +{ >>>>>> + int ret = -ENODEV, i; >>>>>> + struct resource *res; >>>>>> + struct device *dev = &pdev->dev; >>>>>> + struct device_node *np = dev->of_node; >>>>>> + >>>>>> + if (np == NULL) >>>>>> + return 0; >>>>>> + >>>>>> + if (aemif) { >>>>>> + dev_err(dev, "davinci_aemif driver is in use currently\n"); >>>>>> + return -EBUSY; >>>>>> + } >>>>> >>>>> Why expressly prevent multiple AEMIF devices? Its entirely conceivable >>>>> to have two memories like NAND and NOR flash connect to two different >>>>> AEMIF interfaces. >>>>> >>>> Ivan wanted me to clarify the Keystone hardware which supports >>>> 1 instance of controller with 4 CS. That allows already four >>>> devices to be connected. Currently NAND and NOR are connected on it >>>> and two more slots are free. >>>> >>>> Since driver support what hardware is, lets not build a driver for >>>> hardware which don't exist. And if at all such a support would be >>>> needed in future, we can always add it. >>> >>> I understand the lack of hardware part, but its common to write the >>> driver such that it can handle multiple instances. Is there any gain on >>> current hardware because of this check? From what I am hearing, the code >>> in question wont be exercised at all. So why go all the way and add it >>> in first place? >>> >> Fair enough. The check can be dropped. > > Hmm, while the sentiment expressed by Sekhar is noble (to avoid > unnecessarily constraining the driver), removing the check is not > enough. You're still using a global static variable 'aemif', and it is > important not to accidentally re-use this struct if a second device ever > becomes available. So for the current implementation, the check is > necessary IMO. If instead, you were to make 'aemif' a per-device struct > (like with platform_set_drvdata()), then you would not have this issue. > > Brian >
Yes, that is the plan to make it a per-device.
-- Regards, Ivan Khoronzhuk
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