RE: [RFC PATCH 1/2] fpga: fpga-mgr: Add readback support

[Appana Durga Kedareswara Rao]

Hi Alan,

	Thanks for the review... 
Please find comments inline... 

<Snip>
> 
> Hi Appana,
> 
> > Inorder to debug issues with fpga's users would like to read the fpga
> > configuration information.
> > This patch adds readback support for fpga configuration data in the
> > framework through debugfs interface.
> >
> > Usage:
> >         cat /sys/kernel/debug/fpga/readback
> 
> Two things here: I'd prefer calling the attribute "image" rather than
> "readback"
> 
> This should be an entry per fpga manager, not one entry for the whole
> framework, so
> 
> cat /sys/kernel/debug/fpga/fpga0/image

Sure will fix in v2... 

> 
> >
> > Signed-off-by: Appana Durga Kedareswara rao
> > <appana.durga.rao@xxxxxxxxxx>
> > ---
> >  drivers/fpga/fpga-mgr.c       | 52
> +++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/fpga/fpga-mgr.h |  6 +++++
> >  2 files changed, 58 insertions(+)
> >
> > diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c index
> > 9939d2c..7a9fd7c 100644
> > --- a/drivers/fpga/fpga-mgr.c
> > +++ b/drivers/fpga/fpga-mgr.c
> > @@ -484,6 +484,39 @@ void fpga_mgr_put(struct fpga_manager *mgr)  }
> > EXPORT_SYMBOL_GPL(fpga_mgr_put);
> >
> > +#ifdef CONFIG_DEBUG_FS
> > +#include <linux/debugfs.h>
> > +
> > +static int fpga_mgr_read(struct seq_file *s, void *data) {
> > +       struct fpga_manager *mgr = (struct fpga_manager *)s->private;
> > +       int ret = 0;
> 
> Here you should return an error for mgr's that don't support read function:
> 
> if (!mgr->mops->read)
>     return -ENOENT;

Will fix in v2...

> 
> Then you probably should lock the mgr so that nobody tries to write it while
> you are reading.  If you can't lock it, return -EBUSY.

Ok sure will fix in v2... 

> 
> > +
> > +       if (mgr->state != FPGA_MGR_STATE_OPERATING)
> > +               return -EBUSY;
> 
> If the FPGA isn't programmed, I'm not sure that EBUSY would be the correct
> error.

Ok, Should I return EPERM (or) EAGAIN here??? 

> 
> > +
> > +       /* Read the FPGA configuration data from the fabric */
> > +       ret = mgr->mops->read(mgr, s);
> > +       if (ret) {
> > +               dev_err(&mgr->dev, "Error while reading configuration data from
> FPGA\n");
> > +               return ret;
> 
> Don't need this return here since we return right afterwards anyway.

Will fix in v2...

> 
> > +       }
> > +
> > +       return ret;
> > +}
> > +
> > +static int fpga_mgr_read_open(struct inode *inode, struct file *file)
> > +{
> > +       return single_open(file, fpga_mgr_read, inode->i_private); }
> > +
> > +static const struct file_operations fpga_mgr_debugops = {
> 
> Suggest including the name of the debugfs file in the name since more
> debugfs files will be added over time, so
> 
> s/fpga_mgr_debugops/fpga_mgr_ops_image/ or something.

Sure will use fpga_mgr_ops_image 

> 
> > +       .owner = THIS_MODULE,
> > +       .open = fpga_mgr_read_open,
> > +       .read = seq_read,
> > +};
> > +#endif
> > +
> >  /**
> >   * fpga_mgr_lock - Lock FPGA manager for exclusive use
> >   * @mgr:       fpga manager
> > @@ -581,6 +614,21 @@ int fpga_mgr_register(struct device *dev, const
> char *name,
> >         if (ret)
> >                 goto error_device;
> >
> > +#ifdef CONFIG_DEBUG_FS
> 
> I'd prefer an added config such as CONFIG_FPGA_MGR_DEBUG_FS.

Ok, will add an entry in the Kconfig with the name as you suggested in v2...  

> 
> > +       mgr->dir = debugfs_create_dir("fpga", NULL);
> > +       if (!mgr->dir)
> > +               goto error_device;
> > +
> > +       mgr->parent = mgr->dir;
> > +       mgr->dir = debugfs_create_file("readback", 0644, mgr->parent, mgr,
> > +                                      &fpga_mgr_debugops);
> > +       if (!mgr->dir) {
> > +               debugfs_remove_recursive(mgr->parent);
> > +               mgr->parent = NULL;
> > +               goto error_device;
> > +       }
> > +#endif
> > +
> >         dev_info(&mgr->dev, "%s registered\n", mgr->name);
> >
> >         return 0;
> > @@ -604,6 +652,10 @@ void fpga_mgr_unregister(struct device *dev)
> >
> >         dev_info(&mgr->dev, "%s %s\n", __func__, mgr->name);
> >
> > +#ifdef CONFIG_DEBUG_FS
> > +       debugfs_remove_recursive(mgr->parent);
> > +       mgr->parent = NULL;
> > +#endif
> >         /*
> >          * If the low level driver provides a method for putting fpga into
> >          * a desired state upon unregister, do it.
> > diff --git a/include/linux/fpga/fpga-mgr.h
> > b/include/linux/fpga/fpga-mgr.h index 3c6de23..6013809 100644
> > --- a/include/linux/fpga/fpga-mgr.h
> > +++ b/include/linux/fpga/fpga-mgr.h
> > @@ -114,6 +114,7 @@ struct fpga_image_info {
> >   * @write: write count bytes of configuration data to the FPGA
> >   * @write_sg: write the scatter list of configuration data to the FPGA
> >   * @write_complete: set FPGA to operating state after writing is done
> > + * @read: read FPGA configuration information
> 
> Please add note that the read ops is optional similar to below.

Sure will add notes in v2... 

> 
> >   * @fpga_remove: optional: Set FPGA into a specific state during driver
> remove
> >   * @groups: optional attribute groups.
> >   *
> > @@ -131,6 +132,7 @@ struct fpga_manager_ops {
> >         int (*write_sg)(struct fpga_manager *mgr, struct sg_table *sgt);
> >         int (*write_complete)(struct fpga_manager *mgr,
> >                               struct fpga_image_info *info);
> > +       int (*read)(struct fpga_manager *mgr, struct seq_file *s);
> >         void (*fpga_remove)(struct fpga_manager *mgr);
> >         const struct attribute_group **groups;  }; @@ -151,6 +153,10
> > @@ struct fpga_manager {
> >         enum fpga_mgr_states state;
> >         const struct fpga_manager_ops *mops;
> >         void *priv;
> > +#ifdef CONFIG_DEBUG_FS
> > +       struct dentry *dir;
> > +       struct dentry *parent;
> > +#endif
> >  };
> >
> >  #define to_fpga_manager(d) container_of(d, struct fpga_manager, dev)
> > --
> > 2.7.4
> >
> > --
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> 
> Thanks,
> Alan