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Date:	Sun, 05 Jan 2014 16:04:04 +0100
From:	Rostislav Lisovy <lisovy@...il.com>
To:	Hartley Sweeten <HartleyS@...ionengravers.com>
Cc:	Ian Abbott <abbotti@....co.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"pisa@....felk.cvut.cz" <pisa@....felk.cvut.cz>,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH] comedi: Humusoft MF634 and MF624 DAQ cards driver

Hello Hartley (and Dan);
Thank you for the review. I do agree with most of the things, however I
would like to explain/discuss a few of them...

On Thu, 2014-01-02 at 18:38 +0000, Hartley Sweeten wrote: 
> On Monday, December 30, 2013 6:37 PM, Rostislav Lisovy wrote:
> >
> >  create mode 100644 drivers/staging/comedi/drivers/mf6x4.c
> 
> Hello Rostislav,
> 
> As pointed out by Dan Carpenter, you need to add a change log and
> Signed-off-by lines to this patch.

I agree, the missing Signed-off-by is my mistake. I always thought that
the change log should explain the changes to previous version of the
same patch (when resending the patch). What is the reason to have a
change log in the first version of the patch (everything is a change)?

> 
> Overall this looks pretty good. Comments below.
> 
> > diff --git a/drivers/staging/comedi/Kconfig b/drivers/staging/comedi/Kconfig
> > index bfa27e7..89e25b4 100644
> > --- a/drivers/staging/comedi/Kconfig
> > +++ b/drivers/staging/comedi/Kconfig
> > @@ -884,6 +884,12 @@ config COMEDI_GSC_HPDI
> >  	  To compile this driver as a module, choose M here: the module will be
> >  	  called gsc_hpdi.
> >  
> > +config COMEDI_MF6X4
> > +	tristate "Humusoft MF634 and MF624 DAQ Card support"
> > +	---help---
> > +	  This driver supports both Humusoft MF634 and MF624 Data acquisition
> > +	  cards. The legacy Humusoft MF614 card is not supported.
> > +
> >  config COMEDI_ICP_MULTI
> >  	tristate "Inova ICP_MULTI support"
> >  	---help---
> > diff --git a/drivers/staging/comedi/drivers/Makefile b/drivers/staging/comedi/drivers/Makefile
> > index 94cbd26..9e979a9 100644
> > --- a/drivers/staging/comedi/drivers/Makefile
> > +++ b/drivers/staging/comedi/drivers/Makefile
> > @@ -110,6 +110,7 @@ obj-$(CONFIG_COMEDI_NI_PCIMIO)		+= ni_pcimio.o
> >  obj-$(CONFIG_COMEDI_RTD520)		+= rtd520.o
> >  obj-$(CONFIG_COMEDI_S626)		+= s626.o
> >  obj-$(CONFIG_COMEDI_SSV_DNP)		+= ssv_dnp.o
> > +obj-$(CONFIG_COMEDI_MF6X4)		+= mf6x4.o
> >  
> >  # Comedi PCMCIA drivers
> >  obj-$(CONFIG_COMEDI_CB_DAS16_CS)	+= cb_das16_cs.o
> > diff --git a/drivers/staging/comedi/drivers/mf6x4.c b/drivers/staging/comedi/drivers/mf6x4.c
> > new file mode 100644
> > index 0000000..46c7ce5
> > --- /dev/null
> > +++ b/drivers/staging/comedi/drivers/mf6x4.c
> > @@ -0,0 +1,368 @@
> > +/*
> > + *  comedi/drivers/mf6x4.c
> > + *  Driver for Humusoft MF634 and MF624 Data acquisition cards
> > + *
> > + *  COMEDI - Linux Control and Measurement Device Interface
> > + *  Copyright (C) 2000 David A. Schleef <ds@...leef.org>
> > + *
> > + *  This program is free software; you can redistribute it and/or modify
> > + *  it under the terms of the GNU General Public License as published by
> > + *  the Free Software Foundation; either version 2 of the License, or
> > + *  (at your option) any later version.
> > + *
> > + *  This program is distributed in the hope that it will be useful,
> > + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + *  GNU General Public License for more details.
> > + */
> > +/*
> > + * Driver: mf6x4
> > + * Description: Humusoft MF634 and MF624 Data acquisition card driver
> > + * Devices: Humusoft MF634, Humusoft MF624
> > + * Author: Rostislav Lisovy <lisovy@...il.com>
> > + * Status: works
> > + * Updated:
> > + * Configuration Options: none
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/pci.h>
> > +#include "../comedidev.h"
> > +
> > +/* PCI Vendor ID, Device ID */
> > +#define PCI_VENDOR_ID_HUMUSOFT          		0x186c
> > +#define PCI_DEVICE_ID_MF624				0x0624
> > +#define PCI_DEVICE_ID_MF634				0x0634
> 
> Please put the PCI_VENDOR_ID_* in comedidev.h with the other PCI
> Vendor IDs.
> 
> Also, remove the PCI_DEVICE_ID_* defines and just open code the
> values in the pci_device_id table. The mf6x4_boardid enums provide
> adequate documentation.
> 
> > +
> > +/* Registers present in BAR0 memory region */
> > +#define MF624_GPIOC_reg					0x54
> > +
> > +#define MF6X4_GPIOC_EOLC /* End Of Last Conversion */	(1 << 17)
> > +#define MF6X4_GPIOC_LDAC /* Load DACs */		(1 << 23)
> > +#define MF6X4_GPIOC_DACEN				(1 << 26)
> > +
> > +/* BAR1 registers */
> > +#define MF6X4_DIN_reg					0x10
> > +#define MF6X4_DIN_mask					0xff
> > +#define MF6X4_DOUT_reg					0x10
> > +#define MF6X4_DOUT_mask					0xff
> > +
> > +#define MF6X4_ADSTART_reg				0x20
> > +#define MF6X4_ADDATA_reg				0x00
> > +#define MF6X4_ADDATA_mask				0x3fff
> > +#define MF6X4_ADCTRL_reg				0x00
> > +#define MF6X4_ADCTRL_mask				0xff
> > +
> > +#define MF6X4_DA0_reg					0x20
> > +#define MF6X4_DA1_reg					0x22
> > +#define MF6X4_DA2_reg					0x24
> > +#define MF6X4_DA3_reg					0x26
> > +#define MF6X4_DA4_reg					0x28
> > +#define MF6X4_DA5_reg					0x2a
> > +#define MF6X4_DA6_reg					0x2c
> > +#define MF6X4_DA7_reg					0x2e
> > +#define MF6X4_DA_mask					0x3fff
> > +#define MF6X4_DAC_CHANN_CNT				8
> > +
> > +/* BAR2 registers */
> > +#define MF634_GPIOC_reg					0x68
> 
> Please rename these CamelCase defines (i.e. s/_reg/_REG).

I would not call it CamelCase -- it is more like a suffix. The name is
thus composed of the prefix (MF6X4), the name (same as in the
documentation) and a suffix (saying if this is a register name or a
field in a register or mask, etc.) -- the reason why I use lower case is
that it helps readability.

> 
> > +
> > +/* Make a fault-tolerant mapping from DAC cahnnel id obtained as
> > +an int to real HW-dependent offset value */
> 
> Please follow the CodingStyle for all multi-line comments in this driver.
> 
> > +static unsigned int mf6x4_dac_channels[MF6X4_DAC_CHANN_CNT] = {
> > +	[0] = MF6X4_DA0_reg,
> > +	[1] = MF6X4_DA1_reg,
> > +	[2] = MF6X4_DA2_reg,
> > +	[3] = MF6X4_DA3_reg,
> > +	[4] = MF6X4_DA4_reg,
> > +	[5] = MF6X4_DA5_reg,
> > +	[6] = MF6X4_DA6_reg,
> > +	[7] = MF6X4_DA7_reg,
> > +};
> 
> Is this static global array really needed? How about just,
> 
> #define MF6X4_DA_REG(x)			(0x20 + ((x) * 2))

Not needed at all. I just wanted to make it very "fault-tolerant" but I
agree it is unnecessary overkill.

> 
> > +
> > +enum mf6x4_boardid {
> > +	BOARD_MF634,
> > +	BOARD_MF624,
> > +};
> > +
> > +struct mf6x4_board {
> > +	const char *name;
> > +	unsigned int bar_nums[3]; /* We need to keep track of the
> > +				     order of BARs used by the cards */
> > +};
> > +
> > +static const struct mf6x4_board mf6x4_boards[] = {
> > +	[BOARD_MF634] = {
> > +		.name           = "mf634",
> > +		.bar_nums	= {0, 2, 3},
> > +	},
> > +	[BOARD_MF624] = {
> > +		.name           = "mf624",
> > +		.bar_nums	= {0, 2, 4},
> > +	},
> > +};
> > +
> > +struct mf6x4_private {
> > +	struct pci_dev *pci_dev;
> 
> This private data member does not appear to be used. Please remove it.
> 
> > +
> > +	/* Documentation for both MF634 and MF624 describes registers
> > +	present in BAR0, 1 and 2 regions.
> > +	The real (i.e. in HW) BAR numbers are different for MF624 and
> > +	MF634 yet we will call them 0, 1, 2 */
> > +	void __iomem *bar0_mem;
> > +	void __iomem *bar1_mem;
> > +	void __iomem *bar2_mem;
> > +
> > +	void __iomem *gpioc_reg; /* This configuration register has the same
> > +		content for the both cards however it liess in different BARs
> > +		on different offsets -- this helps to make the access easier */
> > +};
> > +
> > +static int mf6x4_dio_insn_bits(struct comedi_device *dev,
> > +			       struct comedi_subdevice *s,
> > +			       struct comedi_insn *insn, unsigned int *data)
> > +{
> > +	struct mf6x4_private *devpriv = dev->private;
> > +
> > +	switch (s->type) {
> > +	case COMEDI_SUBD_DI: /* DIN */
> > +		data[1] = ioread16(devpriv->bar1_mem + MF6X4_DIN_reg) & MF6X4_DIN_mask;
> > +		break;
> > +
> > +	case COMEDI_SUBD_DO: /* DOUT */
> > +		/* data[0] -- mask
> > +		   data[1] -- actual value */
> > +		if (data[0]) {
> > +			s->state &= ~data[0];
> > +			s->state |= (data[0] & data[1]);
> 
> Please use comedi_dio_update_state() to handle this boilerplate code.
> 
> > +
> > +			iowrite16(s->state & MF6X4_DOUT_mask,
> > +				devpriv->bar1_mem + MF6X4_DOUT_reg);
> > +
> > +			data[1] = s->state;
> > +		}
> > +		break;
> > +	}
> > +
> > +	return insn->n;
> > +}
> 
> Please split this function into a mf6x4_di_insn_bits() and mf6x4_do_insn_bits().
> That will remove an indent level and make the usage a bit clearer.
> 
> > +
> > +static int mf6x4_ai_insn_read(struct comedi_device *dev,
> > +			      struct comedi_subdevice *s,
> > +			      struct comedi_insn *insn, unsigned int *data)
> > +{
> > +	struct mf6x4_private *devpriv = dev->private;
> > +	unsigned int chan = CR_CHAN(insn->chanspec);
> > +	unsigned int timeout = 100;
> > +	unsigned int eolc;
> > +	unsigned int n;
> > +	unsigned int i;
> > +	int d;
> > +
> > +	/* Set the ADC channel number in the scan list */
> > +	iowrite16((1 << chan) & MF6X4_ADCTRL_mask,
> > +		devpriv->bar1_mem + MF6X4_ADCTRL_reg);
> > +
> > +	for (n = 0; n < insn->n; n++) {
> > +		/* Trigger ADC conversion by reading ADSTART */
> > +		ioread16(devpriv->bar1_mem + MF6X4_ADSTART_reg);
> > +
> > +		/* Wait until the conversion finishes or times out */
> > +		for (i = 0; i < timeout; i++) {
> > +			eolc = ioread32(devpriv->gpioc_reg) & MF6X4_GPIOC_EOLC;
> > +
> > +			if (!eolc)
> > +				break;
> > +		}
> > +		if (i == timeout) {
> > +			dev_warn(dev->class_dev, "ADC conversion timed out\n");
> > +			return -ETIMEDOUT;
> > +		}
> 
> Please factor out the timeout loop as a helper function. See pcl711.c for an
> example.
> 
> > +
> > +		/* Read the actual value */
> > +		d = ioread16(devpriv->bar1_mem + MF6X4_ADDATA_reg);
> > +		d &= MF6X4_ADDATA_mask;
> 
> This could just be:
> 
> 		d &= s->maxdata;
> 
> > +		data[n] = d;
> > +	}
> > +
> > +	iowrite16(0x0, devpriv->bar1_mem + MF6X4_ADCTRL_reg);
> > +
> > +	return n;
> 
> 	return insn->n;
> 
> > +}
> > +
> > +static int mf6x4_ao_insn_write(struct comedi_device *dev,
> > +			       struct comedi_subdevice *s,
> > +			       struct comedi_insn *insn, unsigned int *data)
> > +{
> > +	struct mf6x4_private *devpriv = dev->private;
> > +	int chan = CR_CHAN(insn->chanspec);
> > +	uint32_t gpioc;
> > +	int i;
> > +
> > +	chan = (chan < MF6X4_DAC_CHANN_CNT) ? chan : 0;
> > +
> > +	/* Enable instantaneous update of converters outputs + Enable DACs */
> > +	gpioc = ioread32(devpriv->gpioc_reg);
> > +	iowrite32((gpioc & ~MF6X4_GPIOC_LDAC) | MF6X4_GPIOC_DACEN, devpriv->gpioc_reg);
> > +
> > +	/* Writing a list of values to an AO channel is probably not
> > +	   very useful, but that's how the interface is defined. */
> 
> Please remove the comment above.
> 
> > +	for (i = 0; i < insn->n; i++) {
> > +		iowrite16(data[i] & MF6X4_DA_mask,
> > +			devpriv->bar1_mem + mf6x4_dac_channels[chan]);
> > +	}
> 
> You should provide an (*insn_read) for the analog output subdevice.
> The last data written to the channel can be cached in the private data.
> 
> Something like:
> 
> 	unsigned int val = devpriv->ao_readback[chan];
> 
> 	for (i = 0; i < insn->n; i++) {
> 		val = data[i];
> 		val &= s->maxdata;
> 
> 		iowrite16(val, devpriv->bar1_mem + MF6X4_DA_REG(chan));
> 	}
> 	devpriv->ao_readback[chan] = val;
> 
> > +
> > +	return i;
> 
> 	return insn->n;
> 
> > +}
> > +
> > +static int mf6x4_auto_attach(struct comedi_device *dev, unsigned long context)
> > +{
> > +	struct pci_dev *pcidev = comedi_to_pci_dev(dev);
> > +	const struct mf6x4_board *board = NULL;
> > +	struct mf6x4_private *devpriv;
> > +	struct comedi_subdevice *s;
> > +	int ret;
> > +
> > +	if (context < ARRAY_SIZE(mf6x4_boards))
> > +		board = &mf6x4_boards[context];
> > +	else
> > +		return -ENODEV;
> > +
> > +	dev->board_ptr = board;
> > +	dev->board_name = board->name;
> > +
> > +	ret = comedi_pci_enable(dev); /* pci_enable_device(), pci_request_regions() */
> 
> The comment is not needed.
> 
> > +	if (ret)
> > +		return ret;
> > +
> > +	devpriv = comedi_alloc_devpriv(dev, sizeof(*devpriv));
> > +	if (!devpriv)
> > +		return -ENOMEM;
> > +
> > +	devpriv->bar0_mem = pci_ioremap_bar(pcidev, board->bar_nums[0]);
> > +	if (!devpriv->bar0_mem) {
> > +		dev_err(dev->class_dev, "Failed to remap Device configuration BAR\n");
> > +		ret = -ENODEV;
> 
> Just return the error here and below.

The reason I did it in this way is the comment next to the 'out' label.
For somebody not experienced with comedi drivers (like me or somebody
else reading the code in the future) the sequence of memory allocation
(or 'pci_ioremap_bar') followed by a 'return' statement looks quite
scary. Either I can write the comment to each return or do it with the
single point of exit.

> 
> > +		goto out;
> > +	}
> > +
> > +	devpriv->bar1_mem = pci_ioremap_bar(pcidev, board->bar_nums[1]);
> > +	if (!devpriv->bar1_mem) {
> > +		dev_err(dev->class_dev, "Failed to remap ADC, DAC, DIO BAR\n");
> > +		ret = -ENODEV;
> > +		goto out;
> > +	}
> > +
> > +	devpriv->bar2_mem = pci_ioremap_bar(pcidev, board->bar_nums[2]);
> > +	if (!devpriv->bar2_mem) {
> > +		dev_err(dev->class_dev, "Failed to remap Counter/timer BAR\n");
> > +		ret = -ENODEV;
> > +		goto out;
> > +	}
> > +
> > +	if (board == &mf6x4_boards[BOARD_MF634]) {
> > +		devpriv->gpioc_reg = devpriv->bar2_mem + MF634_GPIOC_reg;
> > +	} else if (board == &mf6x4_boards[BOARD_MF624]) {
> > +		devpriv->gpioc_reg = devpriv->bar0_mem + MF624_GPIOC_reg;
> > +	} else { /* Definitely should not happen */
> > +		devpriv->gpioc_reg = NULL;
> > +	}
> 
> The curly braces are not needed.
> 
> Also, since the else case cannot happen just remove it.
> 
> > +
> > +	ret = comedi_alloc_subdevices(dev, 4);
> > +	if (ret)
> > +		goto out;
> > +
> > +	/* ADC */
> > +	s = &dev->subdevices[0];
> > +	s->type = COMEDI_SUBD_AI;
> > +	s->subdev_flags = SDF_READABLE | SDF_GROUND;
> > +	s->n_chan = 8;
> > +	s->range_table = &range_bipolar10;
> > +	s->maxdata = (1 << 14) - 1;	/* 14 bits ADC */
> 
> 	s->maxdata = 0x3fff;
> 
> > +	s->insn_read = mf6x4_ai_insn_read;
> > +
> > +	/* DAC */
> > +	s = &dev->subdevices[1];
> > +	s->type = COMEDI_SUBD_AO;
> > +	s->subdev_flags = SDF_WRITABLE;
> > +	s->n_chan = 8;
> > +	s->range_table = &range_bipolar10;
> > +	s->maxdata = (1 << 14) - 1;	/* 14 bits DAC */
> 
> 	s->maxdata = 0x3fff;
> 
> > +	s->insn_write = mf6x4_ao_insn_write;
> > +
> > +	/* DIN */
> > +	s = &dev->subdevices[2];
> > +	s->type = COMEDI_SUBD_DI;
> > +	s->subdev_flags = SDF_READABLE;
> > +	s->n_chan = 8;
> > +	s->range_table = &range_digital;
> > +	s->maxdata = 1;
> > +	s->insn_bits = mf6x4_dio_insn_bits;
> > +
> > +	/* DOUT */
> > +	s = &dev->subdevices[3];
> > +	s->type = COMEDI_SUBD_DO;
> > +	s->subdev_flags = SDF_WRITABLE;
> > +	s->n_chan = 8;
> > +	s->range_table = &range_digital;
> > +	s->maxdata = 1;
> > +	s->insn_bits = mf6x4_dio_insn_bits;
> > +
> 
> Please add some whitespace to the subdevice init.
> 
> Nitpick, please reorder the subdevice init as:
> 
> 	s = ...
> 	s->type = ...
> 	s->subdev_flags = ...
> 	s->n_chan = ...
> 	s->maxdata = ...
> 	s-> range_table = ...
> 	s->insn... = ...
> 
> > +	return 0;
> > +
> > +out:
> > +	/* dev->private is freed automatically */
> > +	return ret;
> 
> This should be removed after changing the code above to just return
> the error.
> 
> > +}
> > +
> > +/*
> > + * _detach is called to deconfigure a device. It should deallocate resources.
> > + * This function is also called when _attach() fails, so it should be careful
> > + * not to release resources that were not necessarily allocated by _attach().
> > + * dev->private and dev->subdevices are deallocated automatically by the core.
> > + */
> 
> Please remove this comment.
> 
> > +static void mf6x4_detach(struct comedi_device *dev)
> > +{
> > +	struct mf6x4_private *devpriv = dev->private;
> > +
> > +	if (devpriv->bar0_mem)
> > +		iounmap(devpriv->bar0_mem);
> > +	if (devpriv->bar1_mem)
> > +		iounmap(devpriv->bar1_mem);
> > +	if (devpriv->bar2_mem)
> > +		iounmap(devpriv->bar2_mem);
> > +
> > +	comedi_pci_disable(dev); /* pci_release_regions(), pci_disable_device() */
> > +}
> > +
> > +static struct comedi_driver mf6x4_driver = {
> > +	.driver_name    = "mf6x4",
> > +	.module         = THIS_MODULE,
> > +	.auto_attach    = mf6x4_auto_attach,
> > +	.detach         = mf6x4_detach,
> > +};
> > +
> > +static int mf6x4_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
> > +{
> > +	return comedi_pci_auto_config(dev, &mf6x4_driver, id->driver_data);
> > +}
> > +
> > +static const struct pci_device_id mf6x4_pci_table[] = {
> > +	{ PCI_VDEVICE(HUMUSOFT, PCI_DEVICE_ID_MF634), BOARD_MF634 },
> > +	{ PCI_VDEVICE(HUMUSOFT, PCI_DEVICE_ID_MF624), BOARD_MF624 },
> > +	{ 0 }
> > +};
> > +MODULE_DEVICE_TABLE(pci, mf6x4_pci_table);
> > +
> > +static struct pci_driver mf6x4_pci_driver = {
> > +	.name           = "mf6x4",
> > +	.id_table       = mf6x4_pci_table,
> > +	.probe          = mf6x4_pci_probe,
> > +	.remove         = comedi_pci_auto_unconfig,
> > +};
> > +
> > +module_comedi_pci_driver(mf6x4_driver, mf6x4_pci_driver);
> > +
> > +MODULE_AUTHOR("Rostislav Lisovy <lisovy@...il.com>");
> > +MODULE_DESCRIPTION("Comedi MF634 and MF624 DAQ cards driver");
> > +MODULE_LICENSE("GPL");
> > -- 
> > 1.8.3.2
> 


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