Message-ID: <4D7F5538.6080907@infradead.org>
Date:	Tue, 15 Mar 2011 09:02:00 -0300
From:	Mauro Carvalho Chehab <mchehab@...radead.org>
To:	Florian Mickler <florian@...kler.org>
CC:	oliver@...kum.org, jwjstone@...tmail.fm,
	linux-kernel@...r.kernel.org,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	linux-media@...r.kernel.org,
	Patrick Boettcher <pboettcher@...com.fr>
Subject: Re: [PATCH 01/16] [media] dib0700: get rid of on-stack dma buffers

Em 15-03-2011 05:43, Florian Mickler escreveu:
> usb_control_msg initiates (and waits for completion of) a dma transfer using
> the supplied buffer. That buffer thus has to be seperately allocated on
> the heap.
> 
> In lib/dma_debug.c the function check_for_stack even warns about it:
> 	WARNING: at lib/dma-debug.c:866 check_for_stack
> 
> Note: This change is tested to compile only, as I don't have the hardware.
> 
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=15977.
> Reported-by: Zdenek Kabelac <zdenek.kabelac@...il.com>
> Signed-off-by: Florian Mickler <florian@...kler.org>
> 
> [v2: use preallocated buffer; fix sizeof in one case]
> [v3: use seperate kmalloc mapping for the preallocation,
>      dont ignore errors in probe codepaths  ]
> [v4: minor style nit: functions opening brace goes onto it's own line ]


I'm c/c Patrick, as he is the driver maintainer for those Dibcom drivers.

> ---
>  drivers/media/dvb/dvb-usb/dib0700.h      |    5 +-
>  drivers/media/dvb/dvb-usb/dib0700_core.c |  120 ++++++++++++++++++++++++------
>  2 files changed, 99 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/media/dvb/dvb-usb/dib0700.h b/drivers/media/dvb/dvb-usb/dib0700.h
> index 3537d65..99a1485 100644
> --- a/drivers/media/dvb/dvb-usb/dib0700.h
> +++ b/drivers/media/dvb/dvb-usb/dib0700.h
> @@ -45,8 +45,9 @@ struct dib0700_state {
>  	u8 is_dib7000pc;
>  	u8 fw_use_new_i2c_api;
>  	u8 disable_streaming_master_mode;
> -    u32 fw_version;
> -    u32 nb_packet_buffer_size;
> +	u32 fw_version;
> +	u32 nb_packet_buffer_size;
> +	u8 *buf;
>  };
>  
>  extern int dib0700_get_version(struct dvb_usb_device *d, u32 *hwversion,
> diff --git a/drivers/media/dvb/dvb-usb/dib0700_core.c b/drivers/media/dvb/dvb-usb/dib0700_core.c
> index 98ffb40..1c19b73 100644
> --- a/drivers/media/dvb/dvb-usb/dib0700_core.c
> +++ b/drivers/media/dvb/dvb-usb/dib0700_core.c
> @@ -27,11 +27,17 @@ DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
>  int dib0700_get_version(struct dvb_usb_device *d, u32 *hwversion,
>  			u32 *romversion, u32 *ramversion, u32 *fwtype)
>  {
> -	u8 b[16];
> -	int ret = usb_control_msg(d->udev, usb_rcvctrlpipe(d->udev, 0),
> +	int ret;
> +	u8 *b;
> +
> +	b = kmalloc(16, GFP_KERNEL);
> +	if (!b)
> +		return -ENOMEM;
> +
> +	ret = usb_control_msg(d->udev, usb_rcvctrlpipe(d->udev, 0),
>  				  REQUEST_GET_VERSION,
>  				  USB_TYPE_VENDOR | USB_DIR_IN, 0, 0,
> -				  b, sizeof(b), USB_CTRL_GET_TIMEOUT);
> +				  b, 16, USB_CTRL_GET_TIMEOUT);
>  	if (hwversion != NULL)
>  		*hwversion  = (b[0] << 24)  | (b[1] << 16)  | (b[2] << 8)  | b[3];
>  	if (romversion != NULL)
> @@ -40,6 +46,8 @@ int dib0700_get_version(struct dvb_usb_device *d, u32 *hwversion,
>  		*ramversion = (b[8] << 24)  | (b[9] << 16)  | (b[10] << 8) | b[11];
>  	if (fwtype != NULL)
>  		*fwtype     = (b[12] << 24) | (b[13] << 16) | (b[14] << 8) | b[15];
> +
> +	kfree(b);
>  	return ret;
>  }
>  
> @@ -101,8 +109,19 @@ int dib0700_ctrl_rd(struct dvb_usb_device *d, u8 *tx, u8 txlen, u8 *rx, u8 rxlen
>  
>  int dib0700_set_gpio(struct dvb_usb_device *d, enum dib07x0_gpios gpio, u8 gpio_dir, u8 gpio_val)
>  {
> -	u8 buf[3] = { REQUEST_SET_GPIO, gpio, ((gpio_dir & 0x01) << 7) | ((gpio_val & 0x01) << 6) };
> -	return dib0700_ctrl_wr(d, buf, sizeof(buf));
> +	s16 ret;
> +	u8 *buf = kmalloc(3, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	buf[0] = REQUEST_SET_GPIO;
> +	buf[1] = gpio;
> +	buf[2] = ((gpio_dir & 0x01) << 7) | ((gpio_val & 0x01) << 6);
> +
> +	ret = dib0700_ctrl_wr(d, buf, 3);
> +
> +	kfree(buf);
> +	return ret;
>  }
>  
>  static int dib0700_set_usb_xfer_len(struct dvb_usb_device *d, u16 nb_ts_packets)
> @@ -137,11 +156,12 @@ static int dib0700_i2c_xfer_new(struct i2c_adapter *adap, struct i2c_msg *msg,
>  	   properly support i2c read calls not preceded by a write */
>  
>  	struct dvb_usb_device *d = i2c_get_adapdata(adap);
> +	struct dib0700_state *st = d->priv;
>  	uint8_t bus_mode = 1;  /* 0=eeprom bus, 1=frontend bus */
>  	uint8_t gen_mode = 0; /* 0=master i2c, 1=gpio i2c */
>  	uint8_t en_start = 0;
>  	uint8_t en_stop = 0;
> -	uint8_t buf[255]; /* TBV: malloc ? */
> +	uint8_t *buf = st->buf;
>  	int result, i;
>  
>  	/* Ensure nobody else hits the i2c bus while we're sending our
> @@ -221,6 +241,7 @@ static int dib0700_i2c_xfer_new(struct i2c_adapter *adap, struct i2c_msg *msg,
>  		}
>  	}
>  	mutex_unlock(&d->i2c_mutex);
> +
>  	return i;
>  }
>  
> @@ -231,8 +252,9 @@ static int dib0700_i2c_xfer_legacy(struct i2c_adapter *adap,
>  				   struct i2c_msg *msg, int num)
>  {
>  	struct dvb_usb_device *d = i2c_get_adapdata(adap);
> +	struct dib0700_state *st = d->priv;
>  	int i,len;
> -	u8 buf[255];
> +	u8 *buf = st->buf;
>  
>  	if (mutex_lock_interruptible(&d->i2c_mutex) < 0)
>  		return -EAGAIN;
> @@ -264,8 +286,8 @@ static int dib0700_i2c_xfer_legacy(struct i2c_adapter *adap,
>  				break;
>  		}
>  	}
> -
>  	mutex_unlock(&d->i2c_mutex);
> +
>  	return i;
>  }
>  
> @@ -297,15 +319,23 @@ struct i2c_algorithm dib0700_i2c_algo = {
>  int dib0700_identify_state(struct usb_device *udev, struct dvb_usb_device_properties *props,
>  			struct dvb_usb_device_description **desc, int *cold)
>  {
> -	u8 b[16];
> -	s16 ret = usb_control_msg(udev, usb_rcvctrlpipe(udev,0),
> +	s16 ret;
> +	u8 *b;
> +
> +	b = kmalloc(16, GFP_KERNEL);
> +	if (!b)
> +		return	-ENOMEM;
> +
> +
> +	ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
>  		REQUEST_GET_VERSION, USB_TYPE_VENDOR | USB_DIR_IN, 0, 0, b, 16, USB_CTRL_GET_TIMEOUT);
>  
>  	deb_info("FW GET_VERSION length: %d\n",ret);
>  
>  	*cold = ret <= 0;
> -
>  	deb_info("cold: %d\n", *cold);
> +
> +	kfree(b);
>  	return 0;
>  }
>  
> @@ -313,7 +343,13 @@ static int dib0700_set_clock(struct dvb_usb_device *d, u8 en_pll,
>  	u8 pll_src, u8 pll_range, u8 clock_gpio3, u16 pll_prediv,
>  	u16 pll_loopdiv, u16 free_div, u16 dsuScaler)
>  {
> -	u8 b[10];
> +	s16 ret;
> +	u8 *b;
> +
> +	b = kmalloc(10, GFP_KERNEL);
> +	if (!b)
> +		return -ENOMEM;
> +
>  	b[0] = REQUEST_SET_CLOCK;
>  	b[1] = (en_pll << 7) | (pll_src << 6) | (pll_range << 5) | (clock_gpio3 << 4);
>  	b[2] = (pll_prediv >> 8)  & 0xff; // MSB
> @@ -325,7 +361,10 @@ static int dib0700_set_clock(struct dvb_usb_device *d, u8 en_pll,
>  	b[8] = (dsuScaler >> 8)   & 0xff; // MSB
>  	b[9] =  dsuScaler         & 0xff; // LSB
>  
> -	return dib0700_ctrl_wr(d, b, 10);
> +	ret = dib0700_ctrl_wr(d, b, 10);
> +
> +	kfree(b);
> +	return ret;
>  }
>  
>  int dib0700_ctrl_clock(struct dvb_usb_device *d, u32 clk_MHz, u8 clock_out_gp3)
> @@ -361,11 +400,14 @@ int dib0700_download_firmware(struct usb_device *udev, const struct firmware *fw
>  {
>  	struct hexline hx;
>  	int pos = 0, ret, act_len, i, adap_num;
> -	u8 b[16];
> +	u8 *b;
>  	u32 fw_version;
> -
>  	u8 buf[260];
>  
> +	b = kmalloc(16, GFP_KERNEL);
> +	if (!b)
> +		return -ENOMEM;
> +
>  	while ((ret = dvb_usb_get_hexline(fw, &hx, &pos)) > 0) {
>  		deb_fwdata("writing to address 0x%08x (buffer: 0x%02x %02x)\n",
>  				hx.addr, hx.len, hx.chk);
> @@ -386,7 +428,7 @@ int dib0700_download_firmware(struct usb_device *udev, const struct firmware *fw
>  
>  		if (ret < 0) {
>  			err("firmware download failed at %d with %d",pos,ret);
> -			return ret;
> +			goto out;
>  		}
>  	}
>  
> @@ -407,7 +449,7 @@ int dib0700_download_firmware(struct usb_device *udev, const struct firmware *fw
>  	usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
>  				  REQUEST_GET_VERSION,
>  				  USB_TYPE_VENDOR | USB_DIR_IN, 0, 0,
> -				  b, sizeof(b), USB_CTRL_GET_TIMEOUT);
> +				  b, 16, USB_CTRL_GET_TIMEOUT);
>  	fw_version = (b[8] << 24) | (b[9] << 16) | (b[10] << 8) | b[11];
>  
>  	/* set the buffer size - DVB-USB is allocating URB buffers
> @@ -426,16 +468,21 @@ int dib0700_download_firmware(struct usb_device *udev, const struct firmware *fw
>  			}
>  		}
>  	}
> -
> +out:
> +	kfree(b);
>  	return ret;
>  }
>  
>  int dib0700_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
>  {
>  	struct dib0700_state *st = adap->dev->priv;
> -	u8 b[4];
> +	u8 *b;
>  	int ret;
>  
> +	b = kmalloc(4, GFP_KERNEL);
> +	if (!b)
> +		return -ENOMEM;
> +
>  	if ((onoff != 0) && (st->fw_version >= 0x10201)) {
>  		/* for firmware later than 1.20.1,
>  		 * the USB xfer length can be set  */
> @@ -443,7 +490,7 @@ int dib0700_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
>  			st->nb_packet_buffer_size);
>  		if (ret < 0) {
>  			deb_info("can not set the USB xfer len\n");
> -			return ret;
> +			goto out;
>  		}
>  	}
>  
> @@ -468,7 +515,10 @@ int dib0700_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
>  
>  	deb_info("data for streaming: %x %x\n", b[1], b[2]);
>  
> -	return dib0700_ctrl_wr(adap->dev, b, 4);
> +	ret = dib0700_ctrl_wr(adap->dev, b, 4);
> +out:
> +	kfree(b);
> +	return ret;
>  }
>  
>  int dib0700_change_protocol(struct rc_dev *rc, u64 rc_type)
> @@ -650,6 +700,7 @@ static int dib0700_probe(struct usb_interface *intf,
>  		const struct usb_device_id *id)
>  {
>  	int i;
> +	int ret;
>  	struct dvb_usb_device *dev;
>  
>  	for (i = 0; i < dib0700_device_count; i++)
> @@ -658,8 +709,10 @@ static int dib0700_probe(struct usb_interface *intf,
>  			struct dib0700_state *st = dev->priv;
>  			u32 hwversion, romversion, fw_version, fwtype;
>  
> -			dib0700_get_version(dev, &hwversion, &romversion,
> +			ret = dib0700_get_version(dev, &hwversion, &romversion,
>  				&fw_version, &fwtype);
> +			if (ret < 0)
> +				goto out;
>  
>  			deb_info("Firmware version: %x, %d, 0x%x, %d\n",
>  				hwversion, romversion, fw_version, fwtype);
> @@ -673,18 +726,37 @@ static int dib0700_probe(struct usb_interface *intf,
>  			else
>  				dev->props.rc.core.bulk_mode = false;
>  
> -			dib0700_rc_setup(dev);
> +			ret = dib0700_rc_setup(dev);
> +			if (ret)
> +				goto out;
> +
> +			st->buf = kmalloc(255, GFP_KERNEL);
> +			if (!st->buf) {
> +				ret = -ENOMEM;
> +				goto out;
> +			}

You're allocating a buffer for URB control messages. IMO, this is a good idea, as
this way, allocating/freeing on each urb call is avoided. However, on most places,
you're not using it. The better would be to just use this buffer on all
the above places.

You should just take care of protecting such buffer with a mutex, to avoid concurrency.
Such kind of protection is generally ok, as dvb applications generally serialize
the calls anyway.



>  
>  			return 0;
> +out:
> +			dvb_usb_device_exit(intf);
> +			return ret;
>  		}
>  
>  	return -ENODEV;
>  }
>  
> +static void dib0700_disconnect(struct usb_interface *intf)
> +{
> +	struct dvb_usb_device *d = usb_get_intfdata(intf);
> +	struct dib0700_state *st = d->priv;
> +	kfree(st->buf);
> +	dvb_usb_device_exit(intf);
> +}
> +
>  static struct usb_driver dib0700_driver = {
>  	.name       = "dvb_usb_dib0700",
>  	.probe      = dib0700_probe,
> -	.disconnect = dvb_usb_device_exit,
> +	.disconnect = dib0700_disconnect,
>  	.id_table   = dib0700_usb_id_table,
>  };
>  

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