Re: [PATCH v3 1/3] fpga: mgr: Use standard dev_release for class driver

[Russ Weight <russell.h.weight@intel.com>]

Hi Tom,

On 5/24/21 1:16 PM, Tom Rix wrote:
> Russ,
>
> I think the signature fpga_mgr_register, should change to
>
> int fpga_mgr_register(struct device *, const struct fpga_mager_ops *mops, void *priv);
>
> I'll explain below ..
>
> On 5/24/21 11:50 AM, Russ Weight wrote:
>> The FPGA manager class driver data structure is being treated as a
>> managed resource instead of using standard dev_release call-back
>> to release the class data structure. This change removes the
>> managed resource code for the freeing of the class data structure
>> and combines the create() and register() functions into a single
>> register() function.
>>
>> The devm_fpga_mgr_register() function is retained.
>>
>> Signed-off-by: Russ Weight <russell.h.weight@intel.com>
>> ---
>> v3:
>>    - Cleaned up comment header for fpga_mgr_register()
>>    - Fix error return on ida_simple_get() failure
>> v2:
>>    - Restored devm_fpga_mgr_register() functionality, adapted for the combined
>>      create/register functionality.
>>    - All previous callers of devm_fpga_mgr_register() will continue to call
>>      devm_fpga_mgr_register().
>>    - replaced unnecessary ternary operators in return statements with standard
>>      if conditions.
>> ---
>>   drivers/fpga/altera-cvp.c        |  12 +--
>>   drivers/fpga/altera-pr-ip-core.c |   8 +-
>>   drivers/fpga/altera-ps-spi.c     |  10 +-
>>   drivers/fpga/dfl-fme-mgr.c       |  10 +-
>>   drivers/fpga/fpga-mgr.c          | 163 ++++++++-----------------------
>>   drivers/fpga/ice40-spi.c         |  10 +-
>>   drivers/fpga/machxo2-spi.c       |  10 +-
>>   drivers/fpga/socfpga-a10.c       |  16 ++-
>>   drivers/fpga/socfpga.c           |  10 +-
>>   drivers/fpga/stratix10-soc.c     |  15 +--
>>   drivers/fpga/ts73xx-fpga.c       |  10 +-
>>   drivers/fpga/xilinx-spi.c        |  12 +--
>>   drivers/fpga/zynq-fpga.c         |  16 ++-
>>   drivers/fpga/zynqmp-fpga.c       |  10 +-
>>   include/linux/fpga/fpga-mgr.h    |  17 ++--
>>   15 files changed, 112 insertions(+), 217 deletions(-)
>>
>> diff --git a/drivers/fpga/altera-cvp.c b/drivers/fpga/altera-cvp.c
>> index 4e0edb60bfba..b61020ceb0a1 100644
>> --- a/drivers/fpga/altera-cvp.c
>> +++ b/drivers/fpga/altera-cvp.c
>> @@ -652,19 +652,15 @@ static int altera_cvp_probe(struct pci_dev *pdev,
>>       snprintf(conf->mgr_name, sizeof(conf->mgr_name), "%s @%s",
>>            ALTERA_CVP_MGR_NAME, pci_name(pdev));
>>   -    mgr = devm_fpga_mgr_create(&pdev->dev, conf->mgr_name,
>> -                   &altera_cvp_ops, conf);
>> -    if (!mgr) {
>> -        ret = -ENOMEM;
>> +    mgr = fpga_mgr_register(&pdev->dev, conf->mgr_name,
>> +                &altera_cvp_ops, conf);
>> +    if (IS_ERR(mgr)) {
>> +        ret = PTR_ERR(mgr);
>>           goto err_unmap;
>>       }
>>         pci_set_drvdata(pdev, mgr);
>
> This is a wrapper around
>
> dev_set_drvdata()
>
>>   -    ret = fpga_mgr_register(mgr);
>> -    if (ret)
>> -        goto err_unmap;
>> -
>>       return 0;
>>     err_unmap:
>> diff --git a/drivers/fpga/altera-pr-ip-core.c b/drivers/fpga/altera-pr-ip-core.c
>> index 5b130c4d9882..0980e134cc43 100644
>> --- a/drivers/fpga/altera-pr-ip-core.c
>> +++ b/drivers/fpga/altera-pr-ip-core.c
>> @@ -191,11 +191,11 @@ int alt_pr_register(struct device *dev, void __iomem *reg_base)
>>           (val & ALT_PR_CSR_STATUS_MSK) >> ALT_PR_CSR_STATUS_SFT,
>>           (int)(val & ALT_PR_CSR_PR_START));
>>   -    mgr = devm_fpga_mgr_create(dev, dev_name(dev), &alt_pr_ops, priv);
> using the name of the device
>> -    if (!mgr)
>> -        return -ENOMEM;
>> +    mgr = devm_fpga_mgr_register(dev, dev_name(dev), &alt_pr_ops, priv);
>> +    if (IS_ERR(mgr))
>> +        return PTR_ERR(mgr);
> mgr is unused
>>   -    return devm_fpga_mgr_register(dev, mgr);
>> +    return 0;
>>   }
>>   EXPORT_SYMBOL_GPL(alt_pr_register);
>>   diff --git a/drivers/fpga/altera-ps-spi.c b/drivers/fpga/altera-ps-spi.c
>> index 23bfd4d1ad0f..d3f77b0312b2 100644
>> --- a/drivers/fpga/altera-ps-spi.c
>> +++ b/drivers/fpga/altera-ps-spi.c
>> @@ -302,12 +302,12 @@ static int altera_ps_probe(struct spi_device *spi)
>>       snprintf(conf->mgr_name, sizeof(conf->mgr_name), "%s %s",
>>            dev_driver_string(&spi->dev), dev_name(&spi->dev));
> a combo of devices name, is that really necessary ?

I would like to limit the scope of this patch to address:
(1) a populated dev_release function
(2) combining the device_initialize() and device_add() calls into single call
    to device_register()

Changing the name or removing the sysfs name file could have implications for
users who expect it to be there or, worse yet, have a script that looks for it.
I think these could be done in a separate patch if needed.

>>   -    mgr = devm_fpga_mgr_create(&spi->dev, conf->mgr_name,
>> -                   &altera_ps_ops, conf);
>> -    if (!mgr)
>> -        return -ENOMEM;
>> +    mgr = devm_fpga_mgr_register(&spi->dev, conf->mgr_name,
>> +                     &altera_ps_ops, conf);
>> +    if (IS_ERR(mgr))
>> +        return PTR_ERR(mgr);
> mgr is unused
>>   -    return devm_fpga_mgr_register(&spi->dev, mgr);
>> +    return 0;
>>   }
>>     static const struct spi_device_id altera_ps_spi_ids[] = {
>> diff --git a/drivers/fpga/dfl-fme-mgr.c b/drivers/fpga/dfl-fme-mgr.c
>> index d5861d13b306..d71eba817b3b 100644
>> --- a/drivers/fpga/dfl-fme-mgr.c
>> +++ b/drivers/fpga/dfl-fme-mgr.c
>> @@ -308,14 +308,14 @@ static int fme_mgr_probe(struct platform_device *pdev)
>>         fme_mgr_get_compat_id(priv->ioaddr, compat_id);
>>   -    mgr = devm_fpga_mgr_create(dev, "DFL FME FPGA Manager",
>> -                   &fme_mgr_ops, priv);
>> -    if (!mgr)
>> -        return -ENOMEM;
>> +    mgr = devm_fpga_mgr_register(dev, "DFL FME FPGA Manager",
>> +                     &fme_mgr_ops, priv);
> drv name is 'dfl-fme-mgr', is this close enough ?
>> +    if (IS_ERR(mgr))
>> +        return PTR_ERR(mgr);
>>         mgr->compat_id = compat_id;
>>   -    return devm_fpga_mgr_register(dev, mgr);
>> +    return 0;
>>   }
>>     static struct platform_driver fme_mgr_driver = {
>> diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
>> index b85bc47c91a9..22f0dd5c2834 100644
>> --- a/drivers/fpga/fpga-mgr.c
>> +++ b/drivers/fpga/fpga-mgr.c
>> @@ -550,20 +550,20 @@ void fpga_mgr_unlock(struct fpga_manager *mgr)
>>   EXPORT_SYMBOL_GPL(fpga_mgr_unlock);
>>     /**
>> - * fpga_mgr_create - create and initialize a FPGA manager struct
>> + * fpga_mgr_register - create and register a FPGA Manager device
>>    * @dev:    fpga manager device from pdev
>
> nit, space or tab after ':' ? this is inconsistent everywhere.
>
>
>>    * @name:    fpga manager name
>>    * @mops:    pointer to structure of fpga manager ops
>>    * @priv:    fpga manager private data
>>    *
>> - * The caller of this function is responsible for freeing the struct with
>> - * fpga_mgr_free().  Using devm_fpga_mgr_create() instead is recommended.
>> + * The caller of this function is responsible for calling fpga_mgr_unregister().
>> + * Using devm_fpga_mgr_register instead is recommended.
>>    *
>> - * Return: pointer to struct fpga_manager or NULL
>> + * Returns a struct fpga_manager pointer on success, or ERR_PTR() on error.
>>    */
>> -struct fpga_manager *fpga_mgr_create(struct device *dev, const char *name,
>> -                     const struct fpga_manager_ops *mops,
>> -                     void *priv)
>> +struct fpga_manager *
>> +fpga_mgr_register(struct device *dev, const char *name,
>> +          const struct fpga_manager_ops *mops, void *priv)
>>   {
>>       struct fpga_manager *mgr;
>>       int id, ret;
>> @@ -572,21 +572,23 @@ struct fpga_manager *fpga_mgr_create(struct device *dev, const char *name,
>>           !mops->write_init || (!mops->write && !mops->write_sg) ||
>>           (mops->write && mops->write_sg)) {
>>           dev_err(dev, "Attempt to register without fpga_manager_ops\n");
>> -        return NULL;
>> +        return ERR_PTR(-EINVAL);
>
> return -EINVAL;
>
> And similar
>
> The user's error checking is simplified to an int check.
>
> The clunky ERR_PTR()/PTR_ERR() can be removed
>
>>       }
>>         if (!name || !strlen(name)) {
>>           dev_err(dev, "Attempt to register with no name!\n");
>> -        return NULL;
>> +        return ERR_PTR(-EINVAL);
>>       }
>>         mgr = kzalloc(sizeof(*mgr), GFP_KERNEL);
>>       if (!mgr)
>> -        return NULL;
>> +        return ERR_PTR(-ENOMEM);
>>         id = ida_simple_get(&fpga_mgr_ida, 0, 0, GFP_KERNEL);
>> -    if (id < 0)
>> +    if (id < 0) {
>> +        ret = id;
>>           goto error_kfree;
>> +    }
>>         mutex_init(&mgr->ref_mutex);
>>   @@ -594,7 +596,6 @@ struct fpga_manager *fpga_mgr_create(struct device *dev, const char *name,
>
> Just use the device name, do not give the user an option and simplify the calling parameters.
>
> mgr->name = dev_name(dev)
>
>>       mgr->mops = mops;
>>       mgr->priv = priv;
>>   -    device_initialize(&mgr->dev);
>>       mgr->dev.class = fpga_mgr_class;
>>       mgr->dev.groups = mops->groups;
>>       mgr->dev.parent = dev;
>> @@ -605,84 +606,6 @@ struct fpga_manager *fpga_mgr_create(struct device *dev, const char *name,
>>       if (ret)
>>           goto error_device;
>>   
>
> The only use of returned mgr seems to be a variant of setting the dev->driver_data = mgr
>
> so just make it the default and don't pass back the ptr.
>
> dev_set_drvdata(dev, mgr);

I also noticed that in most cases the return pointer is not used. I get what
you are saying - it would be a nice simplification if the pointer did not need
to be returned.

However, I believe we are talking about modifying the driver_data for the
parent of the class driver, right? And the parent driver could spawn
multiple class drivers, or sub drivers. Having one of those sub-drivers control
the contents of it's driver-data doesn't feel right. It seems like the parent
driver should have exclusive control over this pointer.

I'm curious what others think...

- Russ

>
> return 0;
>
>
> Tom
>
>