linux-kernel - Re: [PATCH v9 1/7] nvmem: core: Create all cells before adding the nvmem device

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Date:   Fri, 11 Aug 2023 14:11:22 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Robert Marko <robert.marko@...tura.hr>,
        Luka Perkov <luka.perkov@...tura.hr>,
        Michael Walle <michael@...le.cc>, linux-kernel@...r.kernel.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Daniel Golle <daniel@...rotopia.org>,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH v9 1/7] nvmem: core: Create all cells before adding the
 nvmem device

Hi Srinivas,

srinivas.kandagatla@...aro.org wrote on Fri, 11 Aug 2023 12:11:19 +0100:

> On 08/08/2023 08:24, Miquel Raynal wrote:
> > Hi Srinivas,
> > 
> > srinivas.kandagatla@...aro.org wrote on Tue, 8 Aug 2023 07:56:47 +0100:
> >   
> >> On 08/08/2023 07:29, Miquel Raynal wrote:  
> >>> Let's pack all the cells creation in one place, so they are all created
> >>> before we add the nvmem device.
> >>>
> >>> Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> >>> ---
> >>>    drivers/nvmem/core.c | 12 ++++++------
> >>>    1 file changed, 6 insertions(+), 6 deletions(-)
> >>>
> >>> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> >>> index 3f8c7718412b..48659106a1e2 100644
> >>> --- a/drivers/nvmem/core.c
> >>> +++ b/drivers/nvmem/core.c
> >>> @@ -998,12 +998,6 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
> >>>    	if (rval)
> >>>    		goto err_remove_cells;  
> >>>    > -	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);  
> >>> -
> >>> -	rval = device_add(&nvmem->dev);
> >>> -	if (rval)
> >>> -		goto err_remove_cells;
> >>> -
> >>>    	rval = nvmem_add_cells_from_fixed_layout(nvmem);
> >>>    	if (rval)
> >>>    		goto err_remove_cells;
> >>> @@ -1012,6 +1006,12 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
> >>>    	if (rval)
> >>>    		goto err_remove_cells;  
> >>>    > +	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);  
> >>> +
> >>> +	rval = device_add(&nvmem->dev);
> >>> +	if (rval)
> >>> +		goto err_remove_cells;  
> >>
> >> All the error handling paths are now messed up with this patch, put_device() in error path will be called incorrectly from multiple places.  
> > 
> > I'm not sure what this means. Perhaps I should additionally call
> > device_del() after device_add was successful to mimic the
> > device_unregister() call from the remove path. Is that what you mean?  
> 
> 
> This looks perfectly fine, no change required. This also fixes a bug of missing device_del() in err path.
> 
> pl, Ignore my old comments.

nvmem_register() calls device_initialize() and later device_add(),
which is exactly the content of device_register(). Upon error
after device_add(), we currently call device_put(), whereas
device_unregister would call both device_del() and device_put().

I would expect device_del() to be first called upon error before
device_put() *after* device_add() has succeded, no?

> > I also see the layout_np below should be freed before jumping in the
> > error section.  
> 
> you mean missing of_node_put()?

Yes, I need to call of_node_put() before jumping into the error path.

Thanks,
Miquèl