linux-kernel - Re: [RFC PATCH] usb: dwc3: core: allow vendor drivers to check probe status

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Date:	Thu, 17 Jul 2014 12:20:45 -0500
From:	Felipe Balbi <balbi@...com>
To:	Lee Jones <lee.jones@...aro.org>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <kernel@...inux.com>,
	<balbi@...com>, <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <peter.griffin+familyguy@...aro.org>
Subject: Re: [RFC PATCH] usb: dwc3: core: allow vendor drivers to check probe
 status

Hi,

On Thu, Jul 17, 2014 at 06:13:33PM +0100, Lee Jones wrote:
> This patch provides mechanism for subordinate devices to check
> whether the DWC3 core probed successfully or otherwise.  Useful
> if PHYs are required to configure controllers, but aren't yet
> available.  The DWC3 core driver will defer probe if PHYs are
> unavailable, however subordinate DWC3 drivers currently do not
> have any visibility or means to check status - until now.

what's a subordinate DWC3 driver ?

> Another way to do this would be to *_phy_get*(), but if every
> driver did this it would create a high level of code
> duplication.
> 
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>  drivers/usb/dwc3/core.c | 12 ++++++++++++
>  drivers/usb/dwc3/core.h |  1 +
>  2 files changed, 13 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index eb69eb9..171ca52 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -47,6 +47,14 @@
>  
>  /* -------------------------------------------------------------------------- */
>  
> +static bool is_enabled = false;
> +
> +int dwc3_is_enabled(void)
> +{
> +	return is_enabled;
> +}
> +EXPORT_SYMBOL(dwc3_is_enabled);

no, no, no, no. Let me try that again, hello no! You _do_ realise there
are systems with more than one dwc3 instance, right ? And this is the
most fragile possible way of doing this.

You never explained what's a dwc3 subordinate driver, you don't show any
example of how this would be used and why/where does the PHY need to
poke into DWC3. Why isn't probe defer enough for you ? Which platform
are you working on ? what is the problem that you're trying to solve ?

From this patch, all I can is NAK this patch with no mercy, sorry.

-- 
balbi

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