linux-kernel - Re: [PATCH v5 3/9] PCI: endpoint: Pass EPF device ID to the probe function

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Date:   Fri, 2 Jun 2023 08:49:40 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Damien Le Moal <dlemoal@...nel.org>
Cc:     lpieralisi@...nel.org, kw@...ux.com, kishon@...nel.org,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v5 3/9] PCI: endpoint: Pass EPF device ID to the probe
 function

On Fri, Jun 02, 2023 at 08:16:45AM +0900, Damien Le Moal wrote:
> On 6/1/23 23:57, Manivannan Sadhasivam wrote:
> > Currently, the EPF probe function doesn't get the device ID argument needed
> > to correctly identify the device table ID of the EPF device.
> > 
> > When multiple entries are added to the "struct pci_epf_device_id" table,
> > the probe function needs to identify the correct one. This is achieved by
> > modifying the pci_epf_match_id() function to return the match ID pointer
> > and passing it to the driver's probe function.
> > 
> > pci_epf_device_match() function can return bool based on the return value
> > of pci_epf_match_id().
> > 
> > Reviewed-by: Kishon Vijay Abraham I <kishon@...nel.org>
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> 
> [...]
> 
> >  static int pci_epf_device_match(struct device *dev, struct device_driver *drv)
> > @@ -510,8 +510,12 @@ static int pci_epf_device_match(struct device *dev, struct device_driver *drv)
> >  	struct pci_epf *epf = to_pci_epf(dev);
> >  	struct pci_epf_driver *driver = to_pci_epf_driver(drv);
> >  
> > -	if (driver->id_table)
> > -		return pci_epf_match_id(driver->id_table, epf);
> > +	if (driver->id_table) {
> > +		if (pci_epf_match_id(driver->id_table, epf))
> > +			return true;
> > +		else
> > +			return false;
> 
> 		return pci_epf_match_id(driver->id_table, epf) != NULL;
> 
> is simpler. If you do not like this, at least drop the "else" as it is not
> necessary at all.
> 

I settle for simplicity :) Also, there is a theoretical possibility of passing
NULL as the id->name, so doesn't want to rule out that.

> > +	}
> >  
> >  	return !strcmp(epf->name, drv->name);
> >  }
> > @@ -520,13 +524,15 @@ static int pci_epf_device_probe(struct device *dev)
> >  {
> >  	struct pci_epf *epf = to_pci_epf(dev);
> >  	struct pci_epf_driver *driver = to_pci_epf_driver(dev->driver);
> > +	const struct pci_epf_device_id *id;
> >  
> >  	if (!driver->probe)
> >  		return -ENODEV;
> >  
> >  	epf->driver = driver;
> > +	id = pci_epf_match_id(driver->id_table, epf);
> 
> Not sure that the id variable is that useful.
> 

Thought it makes the code clear but looking again, it doesn't hurt to call match
directly in probe. Will change it in next iteration.

- Mani

> >  
> > -	return driver->probe(epf);
> > +	return driver->probe(epf, id);
> >  }
> 
> -- 
> Damien Le Moal
> Western Digital Research
> 

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