linux-kernel - Re: [PATCH v5 2/4] base/platform: Continue on insert

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Message-Id: <20150604075425.BC0E7C406CA@trevor.secretlab.ca>
Date:	Thu, 04 Jun 2015 16:54:25 +0900
From:	Grant Likely <grant.likely@...aro.org>
To:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh+dt@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jakub Sitnicki <jsitnicki@...il.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Mike Travis <travis@....com>,
	Thierry Reding <treding@...dia.com>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Cc:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Subject: Re: [PATCH v5 2/4] base/platform: Continue on insert_resource()
 error

On Tue, 26 May 2015 09:31:24 +0200
, Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
 wrote:
> insert_resource() can fail when the resource added  overlaps
> (partially or fully) with another.
> 
> Device tree and AMBA devices may contain resources that overlap, so they
> could not call platform_device_add (see 02bbde7849e6 ('Revert "of:
> use platform_device_add"'))"
> 
> On the other hand, device trees are released using
> platform_device_unregister(). This function calls platform_device_del(),
> which calls release_resource(), that crashes when the resource has not
> been added with with insert_resource. This was not an issue when the
> device tree could not be modified online, but this is not the case
> anymore.
> 
> This patch let the flow continue when there is an insert error, after
> notifying the user with a dev_err(). r->parent is set to NULL, so
> platform_device_del() knows that the resource was not added, and
> therefore it should not be released.
> 
> Acked-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> ---
>  drivers/base/platform.c | 26 +++++++++++++++-----------
>  1 file changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 46a56f694cec..5a29387e5ff6 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -332,7 +332,7 @@ int platform_device_add(struct platform_device *pdev)
>  		 */
>  		ret = ida_simple_get(&platform_devid_ida, 0, 0, GFP_KERNEL);
>  		if (ret < 0)
> -			goto err_out;
> +			return ret;
>  		pdev->id = ret;
>  		pdev->id_auto = true;
>  		dev_set_name(&pdev->dev, "%s.%d.auto", pdev->name, pdev->id);
> @@ -340,7 +340,7 @@ int platform_device_add(struct platform_device *pdev)
>  	}
>  
>  	for (i = 0; i < pdev->num_resources; i++) {
> -		struct resource *p, *r = &pdev->resource[i];
> +		struct resource *conflict, *p, *r = &pdev->resource[i];
>  		unsigned long type = resource_type(r);
>  
>  		if (r->name == NULL)
> @@ -357,11 +357,14 @@ int platform_device_add(struct platform_device *pdev)
>  				p = &ioport_resource;
>  		}
>  
> -		if (insert_resource(p, r)) {
> -			dev_err(&pdev->dev, "failed to claim resource %d\n", i);
> -			ret = -EBUSY;
> -			goto failed;
> -		}
> +		conflict = insert_resource_conflict(p, r);
> +		if (!conflict)
> +			continue;
> +
> +		dev_err(&pdev->dev,
> +			"ignoring resource %pR (conflicts with %s %pR)\n",
> +			r, conflict->name, conflict);
> +		p->parent = NULL;

I'm pretty sure this is going to break some platforms. I described it in
my earlier email today, but I'll summarize here too since this is the
latest patch set.

Making this change allows the registration of devices to continue, but
it will still break device drivers that do a request_resource() on a
region that another device managed to claim with insert_resource(). The
only way around this is to not do insert_resource() at all, or to remove
the request_resource() from all drivers (not feasible).

I think we have to deal with it by making resource insertion optional.
I'd like to make the default be to do the insertion, and be able to
blacklist platforms that have issues.

g.

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