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From: 'Greg Kroah-Hartman' <gregkh@linuxfoundation.org>
To: David Laight <David.Laight@aculab.com>
Cc: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
	Larry Finger <Larry.Finger@lwfinger.net>,
	Phillip Potter <phil@philpotter.co.uk>,
	Pavel Skripkin <paskripkin@gmail.com>,
	"linux-staging@lists.linux.dev" <linux-staging@lists.linux.dev>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH v7 17/19] staging: r8188eu: shorten calls chain of rtw_read{8,16,32}()
Date: Fri, 17 Sep 2021 17:17:23 +0200	[thread overview]
Message-ID: <YUSxg6LfUsib1P45@kroah.com> (raw)
In-Reply-To: <0331c99f809449e88e5e5be9311aa5a9@AcuMS.aculab.com>

On Fri, Sep 17, 2021 at 03:01:27PM +0000, David Laight wrote:
> From: Greg Kroah-Hartman
> > Sent: 17 September 2021 15:50
> ...
> > > +static int usb_read(struct intf_hdl *intfhdl, u16 addr, void *data, u8 size)
> > > +{
> > > +	struct adapter *adapt = intfhdl->padapter;
> > > +	struct dvobj_priv *dvobjpriv = adapter_to_dvobj(adapt);
> > > +	struct usb_device *udev = dvobjpriv->pusbdev;
> > > +	int status;
> > > +	u8 *io_buf; /* Pointer to I/O buffer */
> > 
> > As you "know" size is not going to be larger than 4 (hint, you should
> > prboably check it), just use bytes off of the stack here, and you can
> > ignore this buffer entirely.  That will hopefully allow you in the
> > future to get rid of that buffer as odds are it will not be needed
> > anymore.
> 
> Isn't that likely to be the buffer that gets dma'd to/from?
> In which case it can't be on-stack.
> Certainly that is a common problem with usb drivers.

Yes it was a problem, which is why the USB core function called here
does not require that and makes sure to allocate the buffer itself so
that all will be fine.

> Give the size of the urb? structure allocated for each transfer
> adding a bounce buffer area in it for short transfers would
> surely be sane.

USB speeds are slow you will never notice the difference for control
messages.

thanks,

greg k-h

  reply	other threads:[~2021-09-17 15:19 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17  7:18 [PATCH v7 00/19] staging: r8188eu: shorten and simplify calls chains Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 01/19] staging: r8188eu: remove usb_{read,write}_mem() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 02/19] staging: r8188eu: remove the helpers of rtw_read8() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 03/19] staging: r8188eu: remove the helpers of rtw_read16() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 04/19] staging: r8188eu: remove the helpers of rtw_read32() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 05/19] staging: r8188eu: remove the helpers of usb_write8() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 06/19] staging: r8188eu: remove the helpers of usb_write16() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 07/19] staging: r8188eu: remove the helpers of usb_write32() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 08/19] staging: r8188eu: remove the helpers of usb_writeN() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 09/19] staging: r8188eu: remove the helpers of usb_read_port() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 10/19] staging: r8188eu: remove the helpers of usb_write_port() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 11/19] staging: r8188eu: remove the helpers of usb_read_port_cancel() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 12/19] staging: r8188eu: remove the helpers of usb_write_port_cancel() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 13/19] staging: r8188eu: remove core/rtw_io.c Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 14/19] staging: r8188eu: remove struct _io_ops Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 15/19] staging: r8188eu: clean up usbctrl_vendorreq() Fabio M. De Francesco
2021-09-17 14:44   ` Greg Kroah-Hartman
2021-09-18 11:13     ` Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 16/19] staging: r8188eu: clean up rtw_read*() and rtw_write*() Fabio M. De Francesco
2021-09-17 14:44   ` Greg Kroah-Hartman
2021-09-17 14:45   ` Greg Kroah-Hartman
2021-09-18 11:41     ` Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 17/19] staging: r8188eu: shorten calls chain of rtw_read{8,16,32}() Fabio M. De Francesco
2021-09-17 14:50   ` Greg Kroah-Hartman
2021-09-17 15:01     ` David Laight
2021-09-17 15:17       ` 'Greg Kroah-Hartman' [this message]
2021-09-18 12:19     ` Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 18/19] staging: r8188eu: shorten calls chain of rtw_write{8,16,32,N}() Fabio M. De Francesco
2021-09-17  7:18 ` [PATCH v7 19/19] staging: r8188eu: remove shared buffer for usb requests Fabio M. De Francesco
2021-09-17 14:55   ` Greg Kroah-Hartman
2021-09-17 15:03     ` Pavel Skripkin
2021-09-17 15:06       ` Pavel Skripkin
2021-09-17 15:18       ` Greg Kroah-Hartman
2021-09-17 15:23         ` Pavel Skripkin
2021-09-17 11:07 ` [PATCH v7 00/19] staging: r8188eu: shorten and simplify calls chains Dan Carpenter

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