linux-kernel - Re: [PATCH] staging: r8188eu: remove unused members of struct xmit

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Message-ID: <5fdeb963-2729-dbc5-3fba-85998e28d8d5@gmail.com>
Date:   Mon, 13 Jul 2020 21:28:58 +0300
From:   Ivan Safonov <insafonov@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     devel@...verdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Nishka Dasgupta <nishkadg.linux@...il.com>,
        Larry Finger <Larry.Finger@...inger.net>,
        Soumyajit Deb <debsoumyajit100@...il.com>
Subject: Re: [PATCH] staging: r8188eu: remove unused members of struct
 xmit_buf

On 7/13/20 5:23 PM, Dan Carpenter wrote:
> On Mon, Jul 13, 2020 at 04:16:07PM +0300, Dan Carpenter wrote:
>> On Sun, Jul 12, 2020 at 03:38:21PM +0300, Ivan Safonov wrote:
>>> Remove unused members of struct xmit_buf: alloc_sz, ff_hwaddr,
>>> dma_transfer_addr, bpending and last.
>>>
>>> Signed-off-by: Ivan Safonov <insafonov@...il.com>
>>> ---
>>>   drivers/staging/rtl8188eu/include/rtw_xmit.h  | 5 -----
>>>   drivers/staging/rtl8188eu/os_dep/xmit_linux.c | 1 -
>>>   2 files changed, 6 deletions(-)
>>>
>>> diff --git a/drivers/staging/rtl8188eu/include/rtw_xmit.h b/drivers/staging/rtl8188eu/include/rtw_xmit.h
>>> index 12d16e98176a..3c03987c81a1 100644
>>> --- a/drivers/staging/rtl8188eu/include/rtw_xmit.h
>>> +++ b/drivers/staging/rtl8188eu/include/rtw_xmit.h
>>> @@ -193,14 +193,9 @@ struct xmit_buf {
>>>   	void *priv_data;
>>>   	u16 ext_tag; /*  0: Normal xmitbuf, 1: extension xmitbuf. */
>>>   	u16 flags;
>>> -	u32 alloc_sz;
>>>   	u32  len;
>>>   	struct submit_ctx *sctx;
>>> -	u32	ff_hwaddr;
>>>   	struct urb *pxmit_urb[8];
>>> -	dma_addr_t dma_transfer_addr;	/* (in) dma addr for transfer_buffer */
>>> -	u8 bpending[8];
>>> -	int last[8];
>>>   };
>>>   
>>>   struct xmit_frame {
>>> diff --git a/drivers/staging/rtl8188eu/os_dep/xmit_linux.c b/drivers/staging/rtl8188eu/os_dep/xmit_linux.c
>>> index 017e1d628461..61ced1160951 100644
>>> --- a/drivers/staging/rtl8188eu/os_dep/xmit_linux.c
>>> +++ b/drivers/staging/rtl8188eu/os_dep/xmit_linux.c
>>> @@ -24,7 +24,6 @@ int rtw_os_xmit_resource_alloc(struct adapter *padapter,
>>>   		return _FAIL;
>>>   
>>>   	pxmitbuf->pbuf = PTR_ALIGN(pxmitbuf->pallocated_buf, XMITBUF_ALIGN_SZ);
>>
>> Not related to this patch but kmalloc always returns data which is at
>> least ARCH_KMALLOC_MINALIGN aligned which is never less than
>> XMITBUF_ALIGN_SZ (4) so this is a no-op.

4-byte alignment for 8-byte pointer (for example void *priv_data) on 
64-bit arch is an _error_. It’s good that kmalloc (and vmalloc) is 
already aligned to 8 bytes.

> 
> The alignment in the driver is pretty crazy because it's all unnecessary
> and so complicated.  Every allocation is 4 bytes extra so we can align
> it later.
> 
> Also every buffer is called "pbuf" which stands for pointer to buffer.
> "pallocated_buf" is not really useful either.
> 
> I tried to look at this to see if we could change the alignment, and
> it's complicated because of the naming and the alignment.
> 
> regards,
> dan carpenter
> 

I have already fixed 4 places with unnecessary alignment, but, alas, 
there is no great desire to test them on real hardware.

Ivan.