Add some helpers to share the constraints of devices while attaching to the dmabuf buffer.
At each attach, the constraints are calculated based on the following: - max_segment_size, max_segment_count, segment_boundary_mask from device_dma_parameters.
In case the attaching device's constraints don't match up, attach() fails.
At detach, the constraints are recalculated based on the remaining attached devices.
Two helpers are added: - dma_buf_get_constraints - which gives the current constraints as calculated during each attach on the buffer till the time, - dma_buf_recalc_constraints - which recalculates the constraints for all currently attached devices for the 'paranoid' ones amongst us.
The idea of this patch is largely taken from Rob Clark's RFC at https://lkml.org/lkml/2012/7/19/285, and the comments received on it.
Cc: Rob Clark robdclark@gmail.com Signed-off-by: Sumit Semwal sumit.semwal@linaro.org --- v3: - Thanks to Russell's comment, remove dma_mask and coherent_dma_mask from constraints' calculation; has a nice side effect of letting us use device_dma_parameters directly to list constraints. - update the debugfs output to show constraint info as well.
v2: split constraints-sharing and allocation helpers
drivers/dma-buf/dma-buf.c | 126 +++++++++++++++++++++++++++++++++++++++++++++- include/linux/dma-buf.h | 7 +++ 2 files changed, 132 insertions(+), 1 deletion(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 5be225c2ba98..f363f1440803 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -264,6 +264,66 @@ static inline int is_dma_buf_file(struct file *file) return file->f_op == &dma_buf_fops; }
+static inline void init_constraints(struct device_dma_parameters *cons) +{ + cons->max_segment_count = (unsigned int)-1; + cons->max_segment_size = (unsigned int)-1; + cons->segment_boundary_mask = (unsigned long)-1; +} + +/* + * calc_constraints - calculates if the new attaching device's constraints + * match, with the constraints of already attached devices; if yes, returns + * the constraints; else return ERR_PTR(-EINVAL) + */ +static int calc_constraints(struct device *dev, + struct device_dma_parameters *calc_cons) +{ + struct device_dma_parameters cons = *calc_cons; + + cons.max_segment_count = min(cons.max_segment_count, + dma_get_max_seg_count(dev)); + cons.max_segment_size = min(cons.max_segment_size, + dma_get_max_seg_size(dev)); + cons.segment_boundary_mask &= dma_get_seg_boundary(dev); + + if (!cons.max_segment_count || + !cons.max_segment_size || + !cons.segment_boundary_mask) { + pr_err("Dev: %s's constraints don't match\n", dev_name(dev)); + return -EINVAL; + } + + *calc_cons = cons; + + return 0; +} + +/* + * recalc_constraints - recalculates constraints for all attached devices; + * useful for detach() recalculation, and for dma_buf_recalc_constraints() + * helper. + * Returns recalculated constraints in recalc_cons, or error in the unlikely + * case when constraints of attached devices might have changed. + */ +static int recalc_constraints(struct dma_buf *dmabuf, + struct device_dma_parameters *recalc_cons) +{ + struct device_dma_parameters calc_cons; + struct dma_buf_attachment *attach; + int ret = 0; + + init_constraints(&calc_cons); + + list_for_each_entry(attach, &dmabuf->attachments, node) { + ret = calc_constraints(attach->dev, &calc_cons); + if (ret) + return ret; + } + *recalc_cons = calc_cons; + return 0; +} + /** * dma_buf_export_named - Creates a new dma_buf, and associates an anon file * with this buffer, so it can be exported. @@ -313,6 +373,9 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops, dmabuf->ops = ops; dmabuf->size = size; dmabuf->exp_name = exp_name; + + init_constraints(&dmabuf->constraints); + init_waitqueue_head(&dmabuf->poll); dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll; dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0; @@ -422,7 +485,7 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, struct device *dev) { struct dma_buf_attachment *attach; - int ret; + int ret = 0;
if (WARN_ON(!dmabuf || !dev)) return ERR_PTR(-EINVAL); @@ -436,6 +499,9 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
mutex_lock(&dmabuf->lock);
+ if (calc_constraints(dev, &dmabuf->constraints)) + goto err_constraints; + if (dmabuf->ops->attach) { ret = dmabuf->ops->attach(dmabuf, dev, attach); if (ret) @@ -448,6 +514,7 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
err_attach: kfree(attach); +err_constraints: mutex_unlock(&dmabuf->lock); return ERR_PTR(ret); } @@ -470,6 +537,8 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) if (dmabuf->ops->detach) dmabuf->ops->detach(dmabuf, attach);
+ recalc_constraints(dmabuf, &dmabuf->constraints); + mutex_unlock(&dmabuf->lock); kfree(attach); } @@ -770,6 +839,56 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr) } EXPORT_SYMBOL_GPL(dma_buf_vunmap);
+/** + * dma_buf_get_constraints - get the *current* constraints of the dmabuf, + * as calculated during each attach(); returns error on invalid inputs + * + * @dmabuf: [in] buffer to get constraints of + * @constraints: [out] current constraints are returned in this + */ +int dma_buf_get_constraints(struct dma_buf *dmabuf, + struct device_dma_parameters *constraints) +{ + if (WARN_ON(!dmabuf || !constraints)) + return -EINVAL; + + mutex_lock(&dmabuf->lock); + *constraints = dmabuf->constraints; + mutex_unlock(&dmabuf->lock); + return 0; +} +EXPORT_SYMBOL_GPL(dma_buf_get_constraints); + +/** + * dma_buf_recalc_constraints - *recalculate* the constraints for the buffer + * afresh, from the list of currently attached devices; this could be useful + * cross-check the current constraints, for exporters that might want to be + * 'paranoid' about the device constraints. + * + * returns error on invalid inputs + * + * @dmabuf: [in] buffer to get constraints of + * @constraints: [out] recalculated constraints are returned in this + */ +int dma_buf_recalc_constraints(struct dma_buf *dmabuf, + struct device_dma_parameters *constraints) +{ + struct device_dma_parameters calc_cons; + int ret = 0; + + if (WARN_ON(!dmabuf || !constraints)) + return -EINVAL; + + mutex_lock(&dmabuf->lock); + ret = recalc_constraints(dmabuf, &calc_cons); + if (!ret) + *constraints = calc_cons; + + mutex_unlock(&dmabuf->lock); + return ret; +} +EXPORT_SYMBOL_GPL(dma_buf_recalc_constraints); + #ifdef CONFIG_DEBUG_FS static int dma_buf_describe(struct seq_file *s) { @@ -801,6 +920,11 @@ static int dma_buf_describe(struct seq_file *s) buf_obj->file->f_flags, buf_obj->file->f_mode, file_count(buf_obj->file), buf_obj->exp_name); + seq_printf(s, "\tConstraints: Seg Count: %08u, Seg Size: %08u", + buf_obj->constraints.max_segment_count, + buf_obj->constraints.max_segment_size); + seq_printf(s, " seg boundary mask: %08lx\n", + buf_obj->constraints.segment_boundary_mask);
seq_puts(s, "\tAttached Devices:\n"); attach_count = 0; diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 694e1fe1c4b4..489ad9b2e5ae 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -34,6 +34,7 @@ #include <linux/wait.h>
struct device; +struct device_dma_parameters; struct dma_buf; struct dma_buf_attachment;
@@ -116,6 +117,7 @@ struct dma_buf_ops { * @ops: dma_buf_ops associated with this buffer object. * @exp_name: name of the exporter; useful for debugging. * @list_node: node for dma_buf accounting and debugging. + * @constraints: calculated constraints of attached devices. * @priv: exporter specific private data for this buffer object. * @resv: reservation object linked to this dma-buf */ @@ -130,6 +132,7 @@ struct dma_buf { void *vmap_ptr; const char *exp_name; struct list_head list_node; + struct device_dma_parameters constraints; void *priv; struct reservation_object *resv;
@@ -211,4 +214,8 @@ void *dma_buf_vmap(struct dma_buf *); void dma_buf_vunmap(struct dma_buf *, void *vaddr); int dma_buf_debugfs_create_file(const char *name, int (*write)(struct seq_file *)); + +int dma_buf_get_constraints(struct dma_buf *, struct device_dma_parameters *); +int dma_buf_recalc_constraints(struct dma_buf *, + struct device_dma_parameters *); #endif /* __DMA_BUF_H__ */