linux-kernel - Re: [PATCH v2] PCI: endpoint: functions: Use kmemdup instead of duplicating its function

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Date:   Mon, 11 Feb 2019 11:18:25 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Wen Yang <wen.yang99@....com.cn>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <zhong.weidong@....com.cn>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Niklas Cassel <niklas.cassel@...s.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Cyrille Pitchen <cyrille.pitchen@...e-electrons.com>
Subject: Re: [PATCH v2] PCI: endpoint: functions: Use kmemdup instead of
 duplicating its function

Hi Lorenzo,

On 08/02/19 5:50 PM, Lorenzo Pieralisi wrote:
> On Thu, Dec 06, 2018 at 08:52:25PM +0800, Wen Yang wrote:
>> kmemdup has implemented the function that kmalloc() + memcpy().
>> We prefer to kmemdup rather than code opened implementation.
>>
>> This issue was detected with the help of coccinelle.
>>
>> Signed-off-by: Wen Yang <wen.yang99@....com.cn>
>> CC: Kishon Vijay Abraham I <kishon@...com>
>> CC: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>> CC: Bjorn Helgaas <bhelgaas@...gle.com>
>> CC: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
>> CC: Niklas Cassel <niklas.cassel@...s.com>
>> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> CC: Cyrille Pitchen <cyrille.pitchen@...e-electrons.com>
>> CC: linux-pci@...r.kernel.org (open list:PCI ENDPOINT SUBSYSTEM)
>> CC: linux-kernel@...r.kernel.org (open list)
>> ---
>>  drivers/pci/endpoint/functions/pci-epf-test.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> Kishon,
> 
> this looks OK to me, anything I am missing ?

For the existing code this might seem the right thing to do but ideally the
memcpy here should be changed to memcpy_fromio/memcpy_toio.

Also later when we plan to use DMA (on the endpoint) for data transfer, we have
to use kzalloc and dma_map_single APIs.

So maybe the right thing would be to just fix it to use memcpy_fromio here.

Thanks
Kishon
> 
> Lorenzo
> 
>> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
>> index 3e86fa3c7da3..8df6c019f8a2 100644
>> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
>> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
>> @@ -169,14 +169,12 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test)
>>  		goto err_addr;
>>  	}
>>  
>> -	buf = kzalloc(reg->size, GFP_KERNEL);
>> +	buf = kmemdup(src_addr, reg->size, GFP_KERNEL);
>>  	if (!buf) {
>>  		ret = -ENOMEM;
>>  		goto err_map_addr;
>>  	}
>>  
>> -	memcpy(buf, src_addr, reg->size);
>> -
>>  	crc32 = crc32_le(~0, buf, reg->size);
>>  	if (crc32 != reg->checksum)
>>  		ret = -EIO;
>> -- 
>> 2.19.1
>>